The chage command in Linux is used to change the user password expiry information. Indeed, as the administrator, you can control at what frequency users have to change their password. It’s mainly dealing with timers and dates then.
The role of the different chage timers might not be clear for everyone though.
I found it simple to explain them with a timeline, centered around the life of the user password. Around this central timeline, you will find the actions required by the user and the administrator.
You will also find this timeline in a PDF file.