Dictionary/List of RP terms
There isn't, really, because different systems have different titles for individuals serving the same role or people use different names/acronyms for stuff. But, that being said, feel free to ask about anything that you find unclear...lots of folks here willing to answer questions...for instance:
GM--Game Master. The narrator/director of the game. Also commonly known as DM (Dungeon Master) or Storyteller, but it seems like every third game system has its own title for this function.
System--The rules-set under which the game operates. This can be a dizzying array of names, on its own...Dungeons and Dragons (we're up to five editions, now, plus the old original boxed sets), Star Wars (which exists in six or seven different incarnations), World of Darkness (old or new...and which particular type of being is central to the story, whether that be Vampire, Werewolf, Mage, etc). To further complicate this one, you can also have Homebrew...which can be a system created from nothing by the GM or can by hybrid conglomerates of rules from various published systems, etc...and Freeform/Guided Freeform...basically, no specific rules except for what the GM declares. Systems are basically used as a method of conflict resolution within the game and keeping track of character development and advancement, and can vary from as simple as flipping a coin to rolling multiple dice and applying an assortment of modifying factors to the results.
As you can see, from that description alone, there's a huge span of potential answers...so it's easiest to get clear answers if you ask specific questions. Don't feel bad about it...all of us were new, somewhere along the line, and had to ask these same questions.