Newbie question...Heat Sinks?

Hi everyone...please don't flame the newbie. I have spent several hours reading past posts, and on dial-up internet this is painful! Please forgive the ignorant question...but what are aluminum heat sinks and if you pull them off circuit boards do they go in their own sort bin or just in with aluminum?

I have tiny boards from power supplies, power cords, remotes, tore apart a camcorder...just very new & trying to maximize the amount of $ I can get ...literally trying to find $ for food...not looking for pity just help in how I can make a few dollars to get me by...