To add to what others have said, the original form was a rebuke: "RTFA", meaning "read the fucking article", directed at people who make ignorant comments without having read the article. I first came across it on Slashdot in the late 90s, but I imagine it may have its roots earlier than that, and possibly from somewhere else.

I think nowadays most people use "TFA" (no leading "R") in a fairly benign way, without the aggressive tone of the original.