Sudo (superuser do) is a Linux/Unix program that allows users to run commands with the security privileges of another user, typically the root user. Sudo provides audit logging, limited user privileges, and session timeout. It is configured through the /etc/sudoers file, which defines which users can run which commands. Sudo is essential for system administration and is a security best practice compared to logging in directly as root. Proper sudo configuration follows the principle of least privilege.