What is the difference between my Inbox and All Mail?

I am a bit confused

I have a Gmail account that I use with Mail. At the top of the menu on the right is my Inbox, and lower on the right, under Gmail, there is an inbox labled "All Mail". This box has 500+ messages in it I'd like to delete. If I delete the messages from the box titled "All Mail" will they also be deleted from the inbox on the top simply titled "Inbox". I know this may be a beginner's question, but I appreciate any help...Thanks!