An ISP (or Internet Service Provider) is a company that enables you to access the Internet. In return for a fee (usually monthly), you will be able to connect to the Internet for either a set number of hours, or you may even be given unlimited access. Once connected, you can browse the World Wide Web, send and receive e-mail, and download files.
The speed at which your data transfers will vary widely, depending on the type of service you choose. Dial up connection is the slowest, and requires the use of a phone line. Broadband connections such as cable or DSL are much faster, although they can be slightly more expensive.
In addition to providing connections for individuals, ISPs also provide access for large companies, supplying them with a direct connection from their network to the Internet.