BOBBERS:  There are several types of bobbers or floats.  Most are brightly colored so you can see them easily.  The reason for using a bobber is to help keep your bait from sinking all the way to the bottom and to let you see when a fish takes your bait.  They are generally used with live bait (earthworms, crickets, shrimp) or natural baits (cheese balls, chicken necks, pieces of hot dogs) and seldom used with artificial baits (plastic worms, spinner baits etc.).  In combination with a weight or sinker, you want to make sure they float about half-exposed in the water, so the weight doesn't sink them entirely.  You adjust the line so that the float can hold the bait off the bottom but normally close to the bottom.  If it goes under, give the fish just a moment to get a good hold of the bait, then lift the rod tip up firmly to set the hook.