Pollination is the method of transferring pollen from the male anther of a flower to the feminine stigma. In tomatoes, pollination is important for fruit manufacturing. With out pollination, the tomato flowers is not going to produce fruit.
There are two most important kinds of pollination: wind pollination and bug pollination. Wind pollination happens when pollen is carried by the wind from one flower to a different. Insect pollination happens when pollen is transferred from one flower to a different by bugs, corresponding to bees, butterflies, and moths.