Cookie和会话如何运作？

I am trying to understand Cookies and sessions professionally, I know that when browser enter a server the server "ask" the browser to "Paste" him self a cookie with "phpsessid" at the client browser cookies folder, Now when we have the "phpsessid" when client enter the server the browser send to the server the "phpsessid" and the server take a look at his tmp folder and if we have a match so it loads back every data he have for this client, but i am kinda confused with all the process.I am trying to understand Cookies and sessions