A wifi dsl router builds up a static dsl connection and shares it to one or more clients. It has an integrated ethernet switch and an integrated wifi accesspoint that you can either connect your client device by wifi and/or by ethernet (LAN) to the router to use the internet connection or share/exchange data within your network. Some routers have some extra functionality like an USB port to integrate a mass-storage device or a printer into the network. They normaly have an integrated firewall to protect your clients,
As a rule an wifi dsl router with two or more wifi antennas (MIMO) has a higher wifi range than an dsl router with only one antenna. An router with visible wifi antennas has a higher range then an router with internal, non-visible antennas.