The Los Angeles Metropolitan Area is composed of many separate cities that are sometimes mistaken as neighborhoods within Los Angeles as well as many neighborhoods that are sometimes mistaken for separate cities. Beverly Hills, for example, is its own city within Los Angeles county (it has its own mayor, police department, and everything), while Hollywood is merely a district within the City of Los Angeles. People from Los Angeles are known as "Angelenos."
Los Angeles is known as the media capital of the world because of the large numbers of movie studios in the city, as well as the numerous television studios and the dynamic music scene that has spawned acts like The Doors, Beck, Eagles, Red Hot Chili Peppers, and many more. The first successful movie filmed in Los Angeles is generally considered to be 1914's "The Birth of a Nation."
There are four main area codes in Los Angeles proper: 213 was the first area code in the city, and now refers only to a small area downtown. The 323 area code forms a circle around the 213 area. 310 refers to west Los Angeles, and has by far the biggest coverage of any of the Los Angeles area codes, stretching as far north as "The Valley" (more on that later) and as far south as the San Pedro bay. The 818 area code refers to "The Valley" alone (including the far northern parts of Los Angeles as well as the suburbs even farther north of that). Other less known area codes include 424 (a recent overlay of 310).
The Los Angeles area has many districts and cities that I'll now try to tackle, though I can't possibly squeeze what people have written entire books about into a small article online. Perhaps the most famous district of Los Angeles is Hollywood, home of the golden age of cinema. While some studios still exist in Hollywood, much of the movie industry has moved out to cheaper areas; nevertheless, Hollywood is still the classic "name" in the movie industry. Nowadays, Hollywood is mostly home to both high-income housing and low-income housing, depending on what part you are in. Generally, the real estate immediately around Hollywood Boulevard and Sunset Boulevard (which run parallel to each other) is expensive, while anything a few blocks down is cheap and sketchy. Hollywood Boulevard itself is nowadays mostly overcrowded with tourists most of the year, who come to observe the infamous "Walk of Fame," which stretches for several miles. The congestion mostly centers around two of Hollywood's biggest attractions, which are very close to each other: Grauman's Chinese Theater (an icon of grand, classic movie palaces) and the mall at Hollywood and Highland (which is built to resemble the set of "Intolerance," another movie directed by D.W. Griffith, the man who directed "Birth of a Nation"). The area around those two points if interest, while touristy, is often somewhat sketchy at night as it is inhabited by transsexuals and strange people dressed in costumes (though I do recommend getting a photo with one of them at least once in your life). Other attractions in Hollywood include the infamous Hollywood Sign, which is technically in the Hollywood Hills (north of Hollywood). The sign can be observed from many points throughout the county, however.
Another famous area in Los Angeles is West Hollywood, which is its own city (it has its own mayor, police department, and everything). Despite the name, it's not techincally related to Hollywood itself, even though it is west of Hollywood. A popular misconception is that natives call this area "WeHo," though I've never heard the term. West Hollywood is most famously home to the "Sunset Strip," a series of blocks on Sunset Boulevard that contains many staples of Los Angeles culture including the Whisky A Go-Go (The Doors had several early shows there), The Viper Room (previously owned by Johnny Depp, actor River Phoenix died there), and many more.
The city of Beverly Hills is one of the more affluent areas in Los Angeles county. Attractions include the multiple Beverly Hills signs that dot the city, around which tourists congregate on weekends and during summers to snap photos. Also in Beverly Hills is the famous Rodeo Drive, a street that plays home to the most chic (and expensive) of designer clothing. There are many, many clothing stores throughout Beverly Hills, many of them more affordable than yet still as chic as the ones on Rodeo.
Santa Monica is another independent city on the coast of Los Angeles where you can find even more shopping down Main Street, which has several quirky, unique stores along with big names like American Apparel. The 3rd Street Promenade is also famous for its stores. Santa Monica is also the location of most of the county's cleaner beaches, as well as some of the nicest weather in the area, due to its seaside location.
Downtown Los Angeles is a district of the city that has several very cool attractions like Dodger Stadium, the Disney Concert Hall, and the Wiltern, though be warned--it is very, very easy to get lost downtown and end up in a very sketchy neighborhood. I highly suggest that nobody goes there unless they're with someone who knows what they're doing, as the neighborhood isn't so tourist-friendly. Other attractions include the tallest building west of Chicago, which is the US Bank Tower.
As far as Orange County goes, there is not much there. The community of Laguna Beach was made famous by the MTV television show, but isn't that interesting of a place in general. The only real interesting thing in Orange County is Disneyland, which is in the city of Anaheim.
North of the bulk of Los Angeles lies the San Fernando Valley, known as just "The Valley" by locals. It is home to the communities of Sherman Oaks, Encino, Van Nuys, and several other places that aren't too interesting to check out. Strangely, since it's a valley, The Valley is usually several degrees warmer or cooler than the rest of the city (you can literally drive for five minutes and experience a ten degree temperature drop).
Yes, Los Angeles is famous for its crime rate, which was the worst in the early 90s, but has since gone down significantly. Cities famous for gang culture in the Los Angeles area include Compton, Watts, and Inglewood, which are all generally south of anything interesting or relevant in the city, so most residents don't go down there.
In terms of public transportation, there is virtually none. The bus system is helpful for residents who are willing to take the time to learn its confusing routes, but most people just take cars everywhere, which is sort of easy thanks to the extensive network of highways that traverses the city. Unfortunately, these highways are often backed up, leading to severe traffic when traveling long distances. Yes, there is a subway system in Los Angeles, but it mostly just covers the downtown area (yet some lines do extend north into The Valley and south into Compton). It's generally considered more of a novelty by people who have cars.
Public education in Los Angeles is considered by some to be a joke, which is partly true. Public high schools in Los Angeles tend to offer very poor educations, though many elementary schools and some middle schools are top-notch. Los Angeles is also home to a private school "scene" perhaps rivaled only by New York City, with dozens of private schools offering superb educations to those whose parents have enough money to spend on them.
I have to mention the weather in Los Angeles, which is bright and sunny about 80% of the time. There is usually a period in late winter when it rains for several days, but other than that rain is very rare and, for that matter, so are clouds. The climate is very dry (we are in a desert, after all), which is pleasant in the summer because the city gets hot but not muggy.
Yes, the air quality in Los Angeles is pretty bad, although it's not too noticeable from breathing alone. However, from certain high points in the city, you can definitely see the smog layer over the Los Angeles basin. At dusk it looks really cool, and it makes for great sunsets!
Generally, Los Angeles is a great place to be if you know what to avoid. While it's hard to get around, it's a great place to visit because of all the fun things to do (concerts, clubs, shopping, etc) and sights to see. Sometimes it's a pain in the ass to live here, but for the most part it's a blast!
(I think that I have the know-how to write about this, considering I'm a NATIVE Angeleno. As in, I hail from the actual city itself, not some lame suburb...)
Person 2: Have you ever been? Most neighborhoods are pretty safe, and there's a lot of cool shit to do.
Person 1: z0mg but what about the earthquakes?!?!?!?
Person 2: They don't happen that often, like once or twice per year. And they're not huge. Sometimes they're kinda fun, actually.
Person 1: aaahhhh whatevverrr Im not goin i'm happy staying hereee in my lame-ass suburb in middle Americcaaaaaa
Person 2: Suit yourself.