There are many pins of various attractions and collectors pins. They can either be collected just by you, or you can trade them with other guests and Cast Members. If you see a Cast Member who is wearing a lanyard, feel free to talk to them, and express your interest in their pins. If you see one you like, feel free to ask them for a trade, you may get a Cast Member Exclusive pin (Hidden Mickey) in return. (Note: If you see a Cast Member wearing a GREEN lanyard, they can only trade with guests aged 12 or younger.) It is common courtesy that during a trade you trade two pins of equal value (i.e. don't trade a simple mickey symbol for an elaborate attraction pin with moving parts). Also, please only (you) trade a pin that they don't have already on their lanyard for one in return. And, if you're trading with a Cast Member, please only 2 trades per guest with each Cast Member.
That being said, I have collected some pretty cool pins over the years, and I've even met Scoop (a character on Main Street who loves pins as much as anyone else, (he's a Cast Member) and he will often trade 1 for 2, and he only has Cast Member exclusive pins for trade. The fun of pin trading is getting pins, and then wearing them around the parks. As well, as expressing interest and seeing other guests and Cast Member's pins.
You'll most likely trade with Cast Members, but you never know if a guest will approach you about them.
One thing my dad did with me was for each attraction I went on I got to receive a pin based on that attraction. It's gotten me on several rides, I know I wouldn't have without knowing that I'd get a pin when I was done. And I now love the attractions.
In short, Pin Trading is fun!
Hope this Helped!
-pwmitch237
Note: See CR Resort Fan 4 Life's link below (.pdf) for the Etiquette guide about Pin Trading.