a sump is just a device that holds extra water the tank, where you place your filters, heaters, protein skimmers, etc to keep the main tank as pretty as possible. also by having extra water, you actually have a healthier tank.
sumps are pretty universal, usually nothing more than a old aquarium, or a rubbermaid container, fitted with baffles to slow down the waters movement through the sump (giving filters more time, to do their job) and to remove little air bubbles (usually from protein skimmers)
as far pictures look under the sticky post, there is at least 1 link to some there.