You also must have a connection to the net. You usually use a modem to connect to an internet provider. A modem is a small box with one cable attached to the computer and another to the telephone jack. The modem communicates between computers. An internet provider is a company that has a big computer on the net.
People call the provider with their modems.
The provider in his turn connects the people to the net. The prices to have a connection differs in different countries. They range from 20 - 50 DM per month. Internet is not just one network. It is a group of different services.