PreContext: These are largely Object Oriented Concepts. I will be giving you examples with respect to a common Object Oriented example. A car.
1. A mutator is a function that changes something about that car.
Example: If you wanted to change the color, you might use the changeColor() function.
2. An accessor is a function that gets something about the car.
Example: If you wanted to retrieve the number of seats within the car, you would run the getSeats() function.
3. Properties are mutable or immutable. Properties of the car that can be changed are mutable properties
Example: Things that can be changed is the color, the tires, windshield wipers etc. changeColor(aColor)
4. Properties of the car that cannot be changed are immutable.
Example: Year the car was made, the number of tires on the car, the model of the car, the manufacturer.
I hope this helps!