RP is when you interact with other players In Character (IC) - in other words you say to them what your character would say. This tends to be done in public areas such as cantinas. A sure sign that people are engaged in RP is that instead of speaking on /General, they are using /Say, so their conversations aren't broadcast across the whole planet. In theory, you can join in any RP in progress, but in practice it can be tricky - look for an RP thread for more information.
And for goodness sake, most of the posters on thus thread, stop being such RP snobs! Who cares what a character's name is unless it's offensive? If you don't want to RP with them, ignore them. Speeders on Fleet don't go into RP areas, so what's the problem? Most non-RPers, when asked politely, will stop disrupting an RP in progress. How about instead of judging and ignoring newbies, who may not have understood what and RP server is and might in addition be trying to play the game in a foreign language, you encourage them in a friendly manner to join in, show them what they are missing and generally enhance their gaming experience? Not suggesting you do it all the time, of course, but to read some of your posts you'd think that RP was somehow a sacred trust and that interlopers should be stoned to death. This is a GAME. Get a grip! Swallow your annoyance, hit ignore, and let people get on with having fun their own way.