There are a number of reasons for smoke - presuming it is coming from the exhaust then often it indicates the engine is burning oil, but there are may other reasons.
Have a mechanic look at it.
Smoke is not the result of overheating unless the engine is on fire.
Overheated engines may steam, but from under the hood. Where is your "smoke" coming from? If you mean the exhaust pipe, it's not because of overheating. If it's white, your cat converter may be fouled, and if it's blue, you're burning oil.
Black or grey smoke is usually gasoline that's leaking onto your hot engine or exhaust. Blue smoke is almost always engine oil burning--again probably on your engine or exhaust. If the smoke is white, then it's actually steam, and that means coolant is leaking.
If you look under your hood, it might be able to see where, exactly, the problem is. Otherwise, you'll want your mechanic to look at it right away, because the problem might be something serious that might damage your engine before long.
