I walk around the house doing odd jobs and such. When does the game time me out? And where will I be when I come back? (Sorry about these questions, every server has differences)
If the server is full or lagging and you are afk, you'll be kicked off (disconnected). When you rejoin you should be where you left off if you haven't died.
when the server isn't full (which doesn't happen much outside of events), or not lagging, AFK doesn't change much. You just sit there. If players try to send you messages, it will let them know you're away.