There are many Linux commands available, but some of the most commonly used and important ones include:

1. ls: Lists the files and directories in the current directory.

2. cd: Changes the current directory to another directory.

3. mkdir: Creates a new directory.

4. rm: Removes a file or directory.

5. cp: Copies files or directories.

6. mv: Moves or renames files or directories.

7. cat: Displays the contents of a file.

8. grep: Searches for a specific pattern or string in a file.

9. tar: Compresses and archives files and directories.

10. sudo: Executes a command as the superuser or with elevated privileges.

11. chmod: Changes the permissions of a file or directory.

12. ping: Tests network connectivity to a specific host.

13. top: Displays system resource usage and process information.

14. ps: Lists the currently running processes.

15. ssh: Connects to a remote server using the Secure Shell (SSH) protocol.

These commands are just a few of the many powerful tools available in Linux. Learning how to use them effectively can help you to be more productive and efficient on the command line.