What is an after-five dress?

I need to know what an after-five dress is. I have just been selected as a delegate for a state pageant and I need to know this. Plus, can you tell me what websites carry the best long evening gowns, prom dresses, or after-five pastel colored dress is? Please! Please! Please. I really need help with this. Where is the best site or store that carry adults or juniors 3/5 small. Please. Thanks