Grafting is the art of attaching a piece of one plant to another in such a way that the two pieces will bond together and become one plant. One plant is used to provide the root system and sometimes the stem, and is commonly known as the rootstock.
If you are daring enough to try your hand at grafting, you will realize a tremendous amount of pride and self satisfaction when you successfully graft your first plant. Grafting is not difficult; it just takes patience and the correct conditions.
A professor at Syracuse University actually took his grafting experiment to a whole new level and created a tree that bears 40 different types of fruit!
Read about it here: http://college.usatoday.com/2015/07/27/syracuse-professor-creates-fruit-tree/