The first time you plugged in and set up your Macintosh, it guided you through the process of typing your name and a password, which essentially created the first user account on your computer. Every Macintosh needs at least one user account, but if you want to share your Macintosh with other people, you'll need to set up additional accounts. You can create four types of user accounts:
Administrator This account allows full access to modifying all parts of the Macintosh, including creating and deleting additional accounts. In addition, only an Administrator account is able to install software. When you unpacked your Macintosh, the first account you created was the Administrator account.
Standard This account allows full access to all parts of the Macintosh with no ability to create, modify, or delete other user accounts. A Standard account cannot install software.
Managed with Parental Controls This account allows restricted access to the Macintosh including time limitations, restricted Internet access, and limited program access.
Guest This account allows access to the Macintosh without requiring a password, but does not allow saving files or customizing any part of the Macintosh.
As a general rule, you probably want to create only one Administrator account on your Macintosh that you control. If you create a second Administrator account, that second account can delete your Administrator account and all your files, too. The only reason to create two Administrator accounts is if you trust another person not to abuse his or her privileges, such as parents using separate Administrator accounts so both can create and monitor their children's accounts.
A Standard account is handy if you want to give someone full access to the Macintosh except for the ability to create, modify, or delete other accounts and install applications system-wide. For example, if you're the most computer-savvy person in your family, you might want to set up an Administrator account for yourself but set up Standard accounts for your spouse and kids.
A Managed with Parental Controls account is useful for tracking and restricting someone's access to your Macintosh. Managed with Parental Controls accounts are commonly used by parents to give their children limited Internet and computer access. (To learn more about creating a Managed with Parental Controls account, see Project 17.)
A Guest account is typically used for a Macintosh that is located in an area where anyone can use it. By eliminating the need for a password, a Guest account gives everyone access to the Macintosh. By refusing to save files or allow customizing of the Macintosh, a Guest account prevents anyone from messing up your computer. You can create only one Guest account on a Macintosh (but you can create an unlimited number of other types of accounts). By default, your Macintosh has already defined a guest account, so you won't have to bother going through the motions to create one unless you delete the default guest account.