I was typing a message and I accidentally deleted it so now I'm too lazy to type it all back.
Basically, Steam is like PSN/Xbox Live but for PC. You can buy games, make friends, chat and know what your friends are doing, go online, and more.
Summer Camp Sale was when a lot of games were on sale. During this period, you could do achievements (games and Steam ones) such as doing an objective in a game or posting a comment on a profile. After you do these achievements, you gain a ticket. Each time you gain a ticket, you are entered in a grand prize drawing to get 10 games on your wishlist for FREE. Along with that, you could also use your tickets to buy prizes for extra content for your games.
A majority of the prizes was to promote Indie games, but there were a couple good prizes. You could redeem a game, costumes for Portal 2/TF2, and skins for another game. The best part was the fact you could gain tickets for FREE and it only took like 5 minutes to get several of them. If you have a Steam account, you should of at least attempted at getting a free game.