In grafting, the plant with the root system is called the scion rootstock cutting, and the portion of the plant with the buds is called the rootstock scion cutting.

In grafting, the plant with desired root system is called the rootstock, and the portion of the plant with the buds is called the scion.

The grafting is a horticultural technique in which parts from two or more plants are joined together to grow as a one single plant.
Rootstock is the plant selected for its roots because it can provide different properties, such as fruit size, or because it is resistant to drought or diseases. 
Scion is the plant selected for its leaves, flowers, fruits or stems.