1. The philosophy of talking candidly and openly and honestly without fear of what others might think.
a. Usually for another's benefit to let them know of something that is usually hard to discuss
b. To let others know that you are talking honestly and sincerely and that what you are expressing is not a joke and that you are unabashedly being true to your own thoughts and feelings
c. Can be used in the sense to affirm what someone is saying as a true, or valid statement and that they are expressing sincere thoughts and opinions. the two are not necessarily always inclusive though
BTW, if you don't know what the comic about up there, the Game Grumps say "Real talk?" a lot.