Archive a message does what?

So I can "archive" my received messages. What exactly means that or does that?  As there is no user "archive" directory, I am wondering what "archive" is actually doing and good for.

Does it mean these messages will not get automatically purged after 3 months? They will stay in my inbox indefinitely?

Thanks for a brief clarification.

Normally the system will delete messages after a set amount of time, however, if you archive a message it will not be deleted by the server.

Thank you Kansha, that answers it :-)

Welcome :)

How can you archive a message? I don't have 'the button'. 

I found it, yes. Thank you so much! Guess we are equal again  One more question: if you want to see an archived message, how does it work?

Firstly, the archived messages are simply "there" in your inbox. They are not marked as archived or anything. Only difference from normal messages is they get not deleted by the server after 3 months of staying in your inbox.

You can sort the messages (not many options though), there is a little choice window on the left hand upper side of your chess.com window.

How do I delete messages? There should be a way and if not, chess.com should have that feature - absolute basic i am sure i am missing something or not seeing an easy existing way

How can I view archive messages again?

There's an Archive tab on the website to see those