what is the difference between a 3 dimensional and 4 dimensional figure

Three dimensions
 When aircraft flying in air, its required minimum three dimensions to represent its position. These three dimensions are latitude, longitude and altitude. Three dimensions can't represent on paper or 2D computer screen.

Four dimensions
 When aircraft flying in air its position can't represent easily by three dimensions. Because it's moving at every moment. So time is also required to explain when aircraft was available at particular position.
So now position represent by latitude, longitude, altitude and time.