Hi. I'm new to this site as well, so maybe I'm not the best person to answer but I've been roleplaying for a while now on a different site. I haven't heard of the word 'favourite set canon', but I'll share some of the other words I've heard of.
RP: Well, this is pretty obvious but it stands for Roleplay.
ORP or OOC: Which basically means that you're talking about something out of character. For example;
AVA
She gasped as Mich punched Amos in the face.
ORP: Dammn, this stuff just got real.
I've seen Rpers use either forms, and I think it is just what you prefer.
FCs: So these are faceclaims. They are pictures Rpers use to show what their characters look like.
Approachable: This just means that other characters can talk to yours. So if you went "ORP: Ava is approachable" that means that other characters may approach your character and try to strike up a conversation with them.
Dead RP: This means that a roleplay is no longer active.
Mary Sues or Gary Stus: This basically refers to a perfect character with no flaw whatsoever. These want to be avoided as they make the Rp expierience less fun.
I may think of more words later on, so I'll post them if I remember any more. Hope this helps!