It is. It's also sometimes known as character generation.Your looking at Character Creation as a one and done act.
The term you're looking for to represent the rest of it is character development. This happens in-game when the character interacts with the other PCs, the NPCs, the setting, and the adventures; and learns about itself in the process. Or dies trying.
Unless the game is play-by-post I certainly don't see forums and posts as representing any part of play whatsoever.Every time I play my character creates changes to the world, the world creates changes to the character, and the characters create changes in each other. There is a social aspect to it both in game and between player/the GM outside the game. On forums and posts. I rarely show up with character that has all their backstory on sesson one or having any real idea of the identity of my characters. ...