The time when most people sleep, but also get drunk, have sex, have parties, playing video games, finishing last minute work, and really not sleep. Not much different from daytime, people wise
Jake:Whatcha do last night?
Jack:Uhh... "Sleep"
Last Night...
Oh yeah, do it you slut!
A cellphone(usually flat and with a touchscreen) which is basically a small, less powerful computer that can fit in your pocket. Used for things like the Internet and for work but also for entertainment in apps such as "Angry Birds" or "Candy Crush"
Jake: Where were you yesterday?
Jack:Uhhh...the gym
Yesterday...
*on smartphone*DAMN YOU GREEN PIGS!
Used in the same way "Hooray!" but in a more sarcastic tone, used to (sarcastically) celebrate mediocre acheivments.
Jake: I made myself a sandwich yesterday.
Jack: Whoop de doo