In a classroom setting, teachers use visual aids to communicate lessons to students. Often an instructor will wish to make notes on a large surface that can be seen by the students for convenience. For many years blackboards served this purpose.
The main disadvantage of blackboards are the mess they create. Chalk dust tends to cling to board surfaces and coat nearby objects. The chalk board runner tends to fill up with dust and must be cleaned periodically, as do the erasers. Chalk tends to erase imperfectly over time, leaving 'ghost writing' on the board that must be washed with cleaner.
The invention of the dry erase board resolved the mess issue. Expo created 'white boards' that are used with special markers. The markers are easily erased, leaving little or no residue behind. The markers do not drop dust onto the runner or create floating particles in the air.
In addition to being clean, Expo dry erase boards allow the user to utilize color in a way that was not possible with blackboards. The variety of colors allows the instructor to color code notes, create easy to understand charts and other projects. The dry erase board is clearly superior to its blackboard counterpart.