Smokers can be small and cheap units that while challenging to control can still produce fantastic barbecue. Legend says that several major barbecue championships have been won by guys using smokers than cost less than $50. Of course you can also get the large full function barbecue rigs that ride on a trailer and cost thousands of dollars. Smokers are usually metal chambers with a side firebox. They have controllable vents and smoke stacks to let you decide on the temperature and quantity of the smoke. I really have to suggest that if you are new to true barbecue that you start small. Not everyone is up to tending fires for 20 hours to get that perfect pork shoulder.
There are also electric smokers than look like small refrigerators, use wood chips for smoke and are heated by an electrical heating element. These give you great convenience and can produce really great barbecue, but again you pay for all that. These units can be large enough to cook for a small army (or a restaurant) or small enough to handle a family's occasional needs. One of the great things about electric smokers is that you can lower the temperature to cold smoke. Cold smoking is what gives you things like smoked salmon. You can also make jerky in these units easily and without tending a fire for several days.