They are quite common. They can occur at the root or sometimes even within the canopy (those branches that seem to grow straight as a rod toward the sky). Either type can sap some food energy from the tree. It is best to get rid of them so the tree can focus it's food supply to the branches you desire to keep and it's trunk. And has been stated, be prepared to deal with this every year. Sometimes twice in a growing season.
Gardening is Zen to me. It takes me far from any stress and pressure and puts me into a peaceful place.