Pro Counter-Strike players are, like their job suggests, really good at Counter-Strike. They are better at Counter-Strike than, say, you (even though I'm sure you are really good). That's why, for the upcoming ESL One Cologne 2014 CS:GO Championship, Valve have arranged a system in which the pros get to play Counter-Strike, and you get to play with stickers.
The Cologne 2014 Pick'Em Challenge event lets you predict the winning teams of each ESL One match. It's a bit like gambling, only there's no money involved. Or, more accurately, there is money involved, but all of it goes to Valve.
To pick a team, you'll need an unused sticker—available from in-game sticker capsules, or from the Steam Marketplace. Once used, each sticker will be locked for the day, but can be reused for future matches.
Do well, and you can earn a Pick'Em Challenge trophy for your Steam profile. Also, the knowledge that you're really good at determining who's really good at Counter-Strike.
Valve have more plans for the event, which they'll be announcing soon.