A router is a networking device which connects two or more networks and forwards data packets between them.
The TP Link or some other brand’s router will enable connecting the residential or office network (LAN) with the internet (WAN). Depending upon the router model, either wired or wireless or both kind of devices are supported on the LAN side allowing computers or devices to be connected to the router through a wired network or a wireless network. On the WAN side, the router can have an Ethernet Port where the incoming internet connection can be terminated.
Some of the routers have the DSL modem functionality allowing a telephone wire from a DSL connection to be connected on the WAN side. Also, there are some router models which support wireless internet connections by providing a USB port where a USB Data Card can be connected or a SIM slot where a SIM card be inserted.