What is the difference between attending the exposition and attending the convention?

The public exposition is a two day event held Saturday and Sunday where the public can come in for a few hours each day to look at the MOCs that are on display and were built by the Convention attendees.
The Private Builder’s Convention is a four day event held Thursday – Sunday where the registered attendees setup their MOC displays, play games, attend presentations, and generally hang out with other AFOLs.