Sitting on and permanently attached to the Internet are business enterprises called Internet Service Providers (ISPs). One of the services that they provide is access to the Internet for individual PCs and small groups of computers.
It is very unlikely that your computer(s) at work or at home will be linked directly to the Internet. So, you need some way of temporarily making that connection. Currently, most individuals or small businesses make a telephone call to their Internet Service Provider who then links them through to the Internet.
This is called dial-up access.