It's a slide which defines the general layout and designs of all PPT slides based upon it. e.g. if your master has a red background, all slides based on that master will have a red background, too. If you now want to take an existing presentation and change the background of all slides from red to blue, you only have to do this once in the master - instead of changing each and every slide individually.
Powerpoint comes with a special type of slide called slide master. The slide master controls certain text characteristics –such as font , size and color called "master text", as well as background color and certain special effects , such as shadowing and bullet style.
The slide master contains text placeholders and placeholders for footers, such as the date , time and the slide number. When you want to make a global change to the look of your slides, you do not have to change each slide individually . Just make the change once on the slide master , and the Powerpoint automatically updates the existing slides and applies the changes to any new slides you add. To change the formatting of the text, select the text in the placeholders and make changes you want. For example, if you change the color of the placeholder text to blue, text on existing and new slides will be changes to blue automatically.
