Part of the reason is that only the root user has the privileges needed to install or remove applications and make other big changes. To install an application as a regular user, the sudo command can give you those root privileges temporarily. You will, however, have to enter your password.

12. passwd

Need to change your password? Then just type this command at the prompt, and it will ask you to type the current password and then a new one.

Keep in mind that the documentation that goes with the Linux distribution you're using can probably help. In , for example, the on the command line is a nice place to learn about the various commands and what you can do with them.

Linux.org's "" tutorial is also a great place to explore.