Multiple Representations is the idea that a physical phenomena can be explored in many different ways. For example, there is the physical representation which models the system with figures and diagrams, such as a free body diagram. There is also the mathematical representation which uses the equation(s) governing the physics of the system. All of the representations can be used together to help us understand and quantify the physical phenomena.

 

Observe the different types of representations for this section below;

Physical Representations explain the features of the situation in a visual way, often with vector representations of physical quantities overlaid a simple diagram or picture of the situation.

A Free Body Diagram of an object on an inclined plane.

Mathematical Representation uses equation(s) to describe the situation.
 
Graphical Representation describes the situation through use of plots and graphs.

A plot of an object sliding down four frictionless ramps; each ramp is at a different angle.

Descriptive Representation is made up enitrely of words or annotations. Think about how you might explain the situation to someone else.
This can be thought of as a word problem. For example, “If Steve places a one kilogram box on a 30 degree slope that is 3m long, how long will it take to reach the bottom is there is no friction?” would be a descriptive representation of a problem with an inclined plane.
Actual Phenomena could be thought of as doing the experiment. For example, if you're asked which of two runners, with different characteristics of their speeds, will win the race, one way to determine that would be to get two runners to run in the described way and see who wins.

This would be a moving company using a ramp to move boxes into their truck rather than lifting dirrectly from the ground to their truck.