The cables you use inside your home and most businesses for networking are twisted pair cables (meaning there are 8 little wires in them that are twisted together to get good signals). These cables are similar to old telephone cables that had six wires.
Most of the time you will see these cables about three to six feet long that are supplied with equipment you receive to use on your network.
The length of these cables can be up to 100 meters long which in American measurements means they can be about 100 yards long. Another way to think of it I they can be about the length of a football field or the length of a soccer field.
The length is the maximum distance they can go between two devices that are powered such as switches, routers, cable modems (actually are routers) and computers. If you have a non-powered device hooking wires together then the total length of the wires on both sides are limited to 100 meters.
You will see those cables call straight through cables, Ethernet cables and network cables.
Fiber optic cables can be up to 60 miles (yes miles) long depending on the type of signal being sent and the type of fiber optic cable.