Social application used for transmitting random pictures and information to people who are already involved in your daily activities and in photos with you, stalkers, and people who either live too far away or have no interest in communicating with you in real life. Other uses include looking up girls from high school and seeing if they're still hot enough to masturbate to, seeing if anyone prettier than you is commenting on your boyfriends page and posting pictures of offspring and grandchildren while secretly thinking that everyone's family but your is ugly.
See also photostalking
Her: So what made you look me up?
Him: I wanted to have sex with every girl I met in school and of the ones who accepted my friends request, you were the only one on messenger.
Her: So what have you been up to?
Him: Just touching myself while I look at your profile pics. Your newest one is hot!
Her: I didn't post any pictures this weekend since I don't have an iPhone and can only check my email when I'm supposed to be doing other things at work.
Him: You appear to be involved in a sexual act while drunk in public with another female. Even though I haven't seen you in years I would like to have intercourse with you and this stranger at the same time.
Her: I was too drunk to remember the photo being taken so everyone I declined their event requests will know I am a lush and a liar. Also, my present and future employers, significant others, and family will see the photo and that will be awkward and embarrassing for everyone!
Him: I'm going to like this photo and comment on your wall so it will appear higher on the news feed for users that select the most popular option over the most recent one. That way more people will see it before you figure out how to un-tag yourself since the layout of facebook has changed so many times.
Her: Facebook is so much fun! It makes me so much less productive and interesting! I can't keep a job, relationship or be on time but my crops never wither and I have lots of people I don't know who depend on me to send then gifts in social games!