Final answer:
A computer usually connects to a router using a network interface card (NIC), which allows it to interface with the network physically.
Step-by-step explanation:
A computer typically connects to a router with the help of a network interface card (NIC). This hardware is found inside the computer or can sometimes be a separate peripheral that is connected externally. The NIC provides the physical interface between the networking cable and the computer's internal bus, and is responsible for facilitating a network connection. It is not a modem, which is a device that modulates and demodulates analog signals for digital data transmission over telephone lines. A repeater is used to extend the range of a network by boosting the signal, and a networked computer refers to another computer connected to the network rather than the method of connection itself.