The most common sander is the Orbital sander, which is often referred to as a finishing sanders.
They are available in three different sizes, 1/4, 1/3 or 1/2 sheet. (sizes in relation to a standard sanding sheet which is 230 x 280mm)
1/4 sheet sanders are also know as Palm Sanders and are ideal for one handed use and for using in confined areas.(Replacement Sheet Size 140 x 115mm)
1/3 sheet sanders are ideal for most sanding jobs around the home and are easy to handle. (Replacement Sheet Size 93 x 230mm)
1/2 sheet sanders are aimed at trade applications where the larger pad size means quicker work. (Replacement Sheet Size 115 x 280mm)