What does media type print

Problem

I am new for css, still I'm trying to learn media types, i can't understand the usage of media type print, can anyone please explain what really does media type print

for an example what happen I use this css

@media print
  {
  p.test {font-weight:bold;}
  }
Problem courtesy of: Chelz Adams

Solution

It causes the CSS to only apply when the document is rendered to a printer … for putting on paper.

A printer

Solution courtesy of: Quentin

Discussion

Intended for paged material and for documents viewed on screen in print preview mode. Please consult the section on paged media for information about formatting issues that are specific to paged media. look at here for full details about media types

Discussion courtesy of: krishna

Suppose I have a webpage having black back color background then during printing It uses lot of ink. So, the thing I have to do is to change the background color to white and font color to black(if using white earlier).
This thing can be done by using

@media print
{
......
......//here write your code which you want during printing
}

this is an example for using @media print(But it have lot of other plus points also).
Yes, you can see the change during print preview

Discussion courtesy of: Anoop Kumar Sharma

This recipe can be found in it's original form on Stack Over Flow.