About correct use and techniques, features to look for etc.

Random-orbit sanders are power sanders that feature a random orbital pattern that helps avoid obvious swirl marks (AKA swirlies or pigtails). They can be corded or uncorded (battery powered).

These are a type of finish sander, for smoothing of wood that has already been made flat by other means and are not intended for heavy material removal or the removal of finish, although they are commonly utilised for both purposes.