[quote=@Mahz]And here are some I don't understand:

- Psychological?
- WorldBuilding? I see this a lot but I'm not quite sure what it means
as a tag. Does is mean the participants are going to  all develop the
world together?

[/quote]

Psychological refers to the idea that the RP will focus on the psyches of the characters and their development more than the actual events of the roleplay, or the plot itself. Frequently combined with horror, the supernatural and mystery. 

You're right about World-building. Sometimes the GM has the whole world figured out already, or a pre-existing setting is used, and the players only contribute the characters they play. An RP in which the GM invites World-building gives players an opportunity to create (part of) the world themselves, often expressed through their character's history and origins.