As well as change orbital characteristics (apogee, perigee, inclination) at reasonably low cost, enabling closer observation of specific portions of Earth, or of objects in space.
Burns at closest approach (perigee) have the largest influence on total orbital characteristics. Burns at furthest approach (apogee) can raise the entire orbit if desired.
Burns at closest approach (perigee) have the largest influence on total orbital characteristics. Burns at furthest approach (apogee) can raise the entire orbit if desired.
(Or so I understand.)