A:Answer A modem is needed to have a single connection from your internet provider. The router branches out the single connection the modem gives into 4 or more possible wired connections and if also wifi enabled allows for wifi connectivity for all those devices as well. So you can purchase both a modem and a router separately or purchase a modem/router all in one. Personally I recommend using the modem/router all in one type device. Been using them about 15 years and have never had issues. Upgraded models 3 times so far. The family has cellphones, tablets, game systems, laptops and printers on connected on wifi and all working great.