A Dog show and TDI/CGC Test?

So I'm taking my dog to a TDI and DGD test on Sunday (therapy dog international and canine good citizen) but I recently found out it is also a dog show with obedience matches and conformation tests. I have NO idea what I need to wear? Also, what is a conformation test? And what can I expect in the obedience classes. I'm really nervous this is my dogs first show and we though all it was was a TDI/CGC test.