See our explanation on the networking home page. The Internet is an international network of computers connected by phone lines. Most people access the Internet through a modem using a service provider such as America Online.
Intranet is another way of saying internal network within a company.
ISP stands for I nternet S ervice P rovider. A domain name is part of an address on the Internet. A firewall is a security measure that consists of computer hardware and software that controls how people access a network. When you are on a network, you can store files on a server so that they can be used by everyone or a select group of users. As an example a Microsoft Word document can be stored on the server, and only designated users can look at the document, but only one person can edit the document at a time.