How do I use it?

After you either shake your head in wondering what I am doing with a computer or have had a good laugh please help me understand what I have and how to use it. I purchased a thunderbolt cable cable and connector thinking this would help me transfer files between two iMAC'.s. I have a new 27" and connected the Thunderbolt connection to my, slightly, older 21.5" iMac. I was thinking of using this to easily transfer files or whatever I could do with the connection. Please enlighten on how best to use this connection. All comment, good or bad, are appreciated.