Learn Vista - Introduction To User Accounts on Windows Vista

A user account is a collection of information that tells Windows which user rights and access permissions a person has on a computer. User accounts make it so that you can share a computer with several people, but still have your own files and settings. Each person accesses their user account with a user name and password.

There are three different kinds of accounts: Standard, Administrator, and Guest.

A standard user account lets a person use most of the capabilities of the computer, but permission from an administrator is required if you want to make changes that affect other users or the security of the computer. When you use a standard account, you can use most programs that are installed on the computer, but you can't install or uninstall software and hardware, delete files that are required for the computer to work, or change settings on the computer that affect other users. If you're using a standard account, some programs might require you to provide an administrator password before you can perform certain tasks.

An administrator account is a user account that lets you make changes that will affect other users. Administrators can change security settings, install software and hardware, and access all files on the computer. Administrators can also make changes to other user accounts. When you set up Windows, you'll be required to create a user account. This account is an administrator account, that allows you to set up your computer and install any programs that you would like to use. Once you have finished setting up your computer, it's recommended that you use a standard user account for your day-to-day computing. It's more secure to use a standard user account instead of an administrator account.

A guest account is an account for users who don't have a permanent account on your computer or domain. It allows people to use your computer without having access to your personal files. People using the guest account can't install software or hardware, change settings, or create a password. You have to turn on the guest account before it can be used.

Tips:
For better privacy and security protection, if someone else wants to make a user account on your computer, it's very wise that you give him a standard user account instead of an administrator account. The standard account can help protect your computer from making changes that affect everyone who uses the computer.

Source: Taken From Windows Vista Documentation