condensation chamber... if thats what its called
Not a problem and don't worry about not knowing something. No one knows it all.
Eventually the charcol in the canister will become saturated and no longer do it's it's job as well, but there is no test to determine whether one is bad or not as far as I know. They do not affect performance except from a weight and looks standpoint. If you go with an aftermarket carb, it wont have the hookups for it either.
Edit: The correct name for it is "Evaporative Emissons Canister" IIRC and in case you were curious.