What does the 'chmod' command do in Linux?

The 'chmod' command in Linux is specifically used to change the permissions of files and directories. Permissions are critical in managing the security and accessibility of files in a Linux environment, allowing users to define who can read, write, or execute a file.

When you use 'chmod', you can specify different types of access for the owner of the file, groups associated with the file, and all other users. For instance, permissions can be modified using symbolic representations (like 'r' for read, 'w' for write, 'x' for execute) or numeric representations (where permissions are indicated by numbers like 7 for full permissions, 6 for read and write, etc.).

Understanding 'chmod' is fundamental for Linux users because it helps in managing security and ensuring that only authorized users can access or modify files, which is key in multi-user systems.

The other mentioned choices encompass different functionalities; for instance, changing file ownership involves using commands like 'chown', moving files to trash is typically managed with GUI actions or specific commands, and comparing files is achieved through commands like 'diff'. Thus, these options do not correctly represent the function of 'chmod'.