Gmail - Label & Archive

Keep your Inbox nice and tidy by labeling and/or archiving your emails once you've dealt with them.  You can label emails, archive them or use the Move To icon to do these simultaneously.  

What is "All Mail"?  This is your archived mail.  This is a storage place for everything you received or sent but never deleted.   Archiving lets you tidy up your inbox by moving message from your inbox into your All Mail label, so you don't have to delete anything.  It's like moving something into a filing cabinet for safekeeping, rather than putting it in the trash can.