Human: What is the difference between a sander and a sanding disc? Assistant: 
A sander is typically used for rough sanding, such as removing paint or rust from metal. A sanding disc is designed to smooth down surfaces, such as wood, plastic, and fiberglass. A sander will generally have coarse grit (e.g. 120 grit) while a sanding disc may have finer grits (e.g. 220 grit).