a term originating from Jamaica that shows understanding....that one has "seen" what you just said.

Or is just as often used as a question (instead of "know what I'm saying?" or "know what I mean?")

to mean to understand something

Reading acknowledgement on facebook chat.

When the person you're talking to click on your name and hypotheoretically read the message you sent her, a small logo "Seen" appears under your words.

It has been the reason of a few breakups, suicides and uninvited sexual intercourses.

When you're on Facebook and someone chats you, but you don't want to talk to them. Except, you can't ignore them anymore because Facebook decided to tell the other person when you saw the message!

to acknowledge something.

it is a response you give when someone tells you something. it means i see or yeh i understand.

seen = "oh i see"