WDS (Wireless Distribution Service) creates a wireless backbone link between multiple access points that are part of the same wireless network. This allows a wireless network to be expanded using multiple access points without the need for a wired backbone to link them, as is traditionally required. The WDS-enabled access points can accept wireless clients (e.g. wireless laptop users) just as traditional APs would.
Also take note of the fact that all repeaters, including this WDS Repeater mode, will sacrifice half of the bandwidth available from the primary router for clients wirelessly connected to the repeater. This is a result of the repeater taking turns talking to not just one partner, but to two, and having to relay the traffic between them. As long as your bandwidth requirements are within this halved bandwidth amount there will be little or no reduction in «speed».