There are a variety of ways people can hook up to the Internet. Many people have an Internet account through their school or work. Many others have service through one of the thousands of Internet Service Providers. You can connect to the Internet in various ways (for example: Modem, DSL, Cable Modem, Wireless Networking, Local Area Networking, a T1 line, a power line, airborne, via satellite, or by interplanetary means).
Typically if you are a home user with a PC you'll use a variety of hardware, software, and network resources to access Internet content.
For home access, you'll dial a phone number on your computer, and your modem will communicate with your Internet Service Providers host, which has a connection to the Internet. In other schemes, you might purchase an Internet direct link right to your computer--this is more expensive, but it puts you right on the Internet. Other people have wireless, mobile access to the Internet.
The Internet isn't the only network in the online world, although has become the place to be in cyberspace.