useradd/usermod/groupadd (user management) commands in linux

This video explains user management in linux, How to add,create, delete users and groups.How to add users to groups. link to PDF used in video: https://drive.google.com/file/d/0B6lwIJrH_EH4bGFqa0ZmSkl5SDA/view?usp=sharing&resourcekey=0-S1J8qBHo1OxmGVj3_WnOyA