"chmod" stands for "change mode" and is a command used in Unix-like operating systems to change the access permissions of files and directories. It allows users to control who can read, write, or execute a particular file or directory.

The chmod command operates on three categories of users:

• Owner: The user who owns the file or directory.

• Group: The group associated with the file or directory.

• Others: All other users who are not the owner and not in the group.

For each of these categories, chmod can assign or remove the following permissions:

• Read (r): Allows reading and listing contents of a file or directory.

• Write (w): Allows modifying or deleting a file, and creating, deleting, or renaming files within a directory.

• Execute (x): Allows executing a file as a program or script, or entering a directory.

The syntax of the chmod command typically follows this format:

chmod [options] mode file(s)

Here, "mode" specifies the permissions to be set, and "file(s)" represents the file or files on which the permissions are to be changed.

Some common examples of using chmod are:

• chmod +x file: Grants execute permission to the file for the owner, group, and others.

• chmod u+w file: Grants write permission to the owner of the file.

• chmod go-r file: Removes read permission from the group and others for the file.