In XCode there's a text key binding ^Y to the "yank" command.
What does "yank" mean? I thought it was to "yank back deleted text" but so far it only "yanks back" text I cut, which means its synonymous with "paste" on windows?
Yes, yanking and pasting are different terms for the same thing. I first learned about it through pico, and it seems that emacs uses the term as well:
http://www.slac.stanford.edu/comp/unix/gnu-info/emacs_13.html#SEC59
Yank inserts the most recent block of text from the kill buffer, which is the CLI equivalent of a clipboard.
Some ways the kill ring is different from the clipboard on OS X: