My modem is a wi-fi dsl modem.what does this mean?
At one time DSL modems were just bridge modems without any actual networking on them (they had no IP and something else had to do PPPoE). Most DSL modems are now modem/routers that handle the PPPoE and give your PC a private IP to better protect it from nasty people on the internet. Many of those only have 1 ethernet port. Yours does that, probably with 4 ethernet ports and WiFi. So you can connect 4 wired devices and wireless devices on your LAN without needing anything else.