Linux is a free and open-source operating system, similar to UNIX. Linux is known for its stability, security, and flexibility, making it a popular choice for servers, desktops, and mobile devices.

One of the key features of Linux is its command-line interface (CLI), which allows users to perform various tasks by entering commands.

Some of the most commonly used Linux commands include:

1. ls – The most frequently used command in Linux to list directories
2. pwd – Print working directory command in Linux
3. cd – Linux command to navigate through directories
4. mkdir – Command used to create directories in Linux
5. mv – Move or rename files in Linux
6. cp – Similar usage as mv but for copying files in Linux
7. rm – Delete files or directories
8. touch – Create blank/empty files
9. ln – Create symbolic links (shortcuts) to other files
10. cat – Display file contents on the terminal
11. clear – Clear the terminal display
12. echo – Print any text that follows the command
13. less – Linux command to display paged outputs in the terminal
14. man – Access manual pages for all Linux commands
15. uname – Linux command to get basic information about the OS
16. whoami – Get the active username
17. tar – Command to extract and compress files in Linux
18. grep – Search for a string within an output
19. head – Return the specified number of lines from the top
20. tail – Return the specified number of lines from the bottom
21. diff – Find the difference between two files
22. cmp – Allows you to check if two files are identical
23. comm – Combines the functionality of diff and cmp
24. sort – Linux command to sort the content of a file while outputting
25. export – Export environment variables in Linux
26. zip – Zip files in Linux
27. unzip – Unzip files in Linux
28. ssh – Secure Shell command in Linux
29. service – Linux command to start and stop services
30. ps – Display active processes
31. kill and killall – Kill active processes by process ID or name
32. df – Display disk filesystem information
33. mount – Mount file systems in Linux
34. chmod – command to change file permissions
35. chown – Command for granting ownership of files or folders
36. ifconfig – Display network interfaces and IP addresses
37. traceroute – Trace all the network hops to reach the destination
38. wget – Direct download files from the internet
39. ufw – Firewall command
40. iptables – Base firewall for all other firewall utilities to interface with
41. apt, pacman, yum, rpm – Package managers depending on the distro
42. sudo – Command to escalate privileges in Linux
43. cal – View a command-line calendar
44. alias – Create custom shortcuts for your regularly used commands
45. dd – Majorly used for creating bootable USB sticks
46. whereis – Locate the binary, source, and manual pages for a command
47. whatis – Find what a command is used for
48. top – View active processes live with their system usage
49. useradd and usermod – Add new user or change existing users’ data
50. passwd – Create or update passwords for existing users

Additionally, Linux also includes a set of advanced commands such as sed, awk, grep, and find which are used for text processing and file manipulation.

These commands are extremely powerful and once mastered, can be used to perform a wide range of tasks. For example, you can use them to view the system information, manage the users, monitor the system’s performance, automate repetitive tasks and much more.

Overall, Linux is a powerful and versatile operating system that offers a wide range of capabilities through its command-line interface. It is a great choice for those who want a stable, secure, and customizable operating system.