As we mentioned earlier in section 1.1, the design of Debian GNU/Linux comes from the Unix operating system. Unlike common desktop operating systems such as DOS, Windows, and MacOS, GNU/Linux is usually found on large servers and multiuser systems.
This means that Debian has features those other operating systems lack. It allows a large number of people to use the same computer at once, as long as each user has his or her own terminal.1.1 To permit many users to work at once, Debian must allow many programs and applications to run simultaneously. This feature is called multitasking.
Much of the power (and complexity) of GNU/Linux systems stems from these two features. For example, the system must have a way to keep users from accidentally deleting each other's files. The operating system also must coordinate the many programs running at once to ensure that they don't all use the same resource, such as a hard drive, at the same time.
If you keep in mind what Debian was originally designed to do, many aspects of it will make a lot more sense. You'll learn to take advantage of the power of these features.