What is a rooter?

A rooster is a male chicken. He is well known crowing at the rising sun.

A rooter is something that roots, whether an animal like a pig, or a tool like a roto-rooter. The Word 'rooter' can mean an enthusiastic devotee of sports.

A rotor is something that rotates. In a car, rotors are metal plates that turn with the wheels and provide surfaces for the brake disc pads to clamp onto. The pads mount onto the calipers and are on each side of the rotors. As the brakes are applied, the disc pads press into the rotors and provide friction for stopping.

If you actually mean a router, that is a way to create or split a computer network to allow access by multiple computers. One of the most common ways is by address translation. The router can take a single internet address and convert it to a series of local addresses. That way, the computers each have a unique address, even though the router connects to the Internet through a single address.