If growing your own fruit is in your landscape plan, you'll need to make sure you've provided an adequate opportunity for pollination to occur. In most cases, you will need to plant at least two of each type of fruit tree. However, fruit set is enhanced even on self-fruitful trees if more than one tree is in the area.
Most fruit trees belong to the group that requires cross-pollination.
These trees not only need pollen from another tree, but the tree must be of a different cultivar. Pollen from its own flowers or those of another tree of the same cultivar will not be able to successfully pollinate the female parts of the flowers, due to incompatible timing. You'll need to do a little homework to find the right mix of cultivars. Extension bulletins and gardening books are good places to find suggested combinations. Even if you have compatible trees in place, other factors can interfere with pollination.