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 define what actions users can perform on a file or directory, such as reading, writing, or executing it. The command allows the user to specify who can access a file (the owner, the group, or all users) and what type of access they can have.

Using 'chmod', you can assign permissions using either numerical values or symbolic representations. For example, a user can set permissions to allow read (r), write (w), and execute (x) access for different user classes by providing the appropriate arguments to the command.

This command plays a crucial role in managing the security of the system, ensuring that only authorized users have access to modify or execute files. Thus, the primary function of 'chmod' is to directly manipulate file permissions, making option B the correct choice.