In fairly modern times people are suposed to give him a white porridge made of rice on a plate outdoors. Closely related to tomten is vätter and huldra, but they usually do not live that close to humans.
A tomte (tomten) usually lives at farms in Sweden. If he is treated with respect he can be very helpful. Tomten is very proud and sensitive. If you make fun of him or in any other way treat him disrespectfully, he will most certainly punish you. An "accident" can happen to you, the cows will give sour milk or the harvest will fail.
It is also the Swedish word for Santa-Claus.