By using a multi-user operating system, different users can share the same computer. They cannot use the computer at the same time, but they can each save their individual settings and come back to them when they need to.
A multi-user operating system allows multiple users to access a computer system at the same time. (Wikipedia)
When one user is working, he or she will have access to his or her files and settings, and not those of the other users. Then the user just logs off, which means signing out without turning off the computer. Then the next person can log on. This is very helpful for families, so that you don’t have to wade through everyone’s documents to find yours. Also, young children can be prevented from accessing inappropriate content.