This week's giveaway is in the Java/Jakarta EE forum. We're giving away four copies of Java EE 8 High Performance and have Romain Manni-Bucau on-line! See The response is almost the exact same thing but send from the server back to the client.
The purpose of the headers is to allow the client and the server to describe the data being sent back and forth and to communicate what each expects from the other.
If you would like to see these headers in action, download and install the LiveHttpHeaders plugin for FireFox. It's a great tool for debugging web development issues.
Here are all the headers that get passed back and forth from browser to server when a request is made to Google (searching for LiveHttpHeaders):