Equatorial region between the Tropic of Cancer and the Tropic of Capricorn. It is characterized by generally warm or hot temperatures year-round, though much variation exists due to altitude and other factors. Temperate zones north and south of the tropics generally have a winter season.
Definition of delimit. 1  transitive verb. : 2  to fix or define the limits of guidelines delimiting his responsibilities an area delimited by woods.
Optimising means maxing out or increasing the efficiency or general performance to bring out the best in something. As for graphics it means that an image should balance out the best quality with a decent and reasonable file size.