Accessor method: A method written for the purpose of seeing the value of a private field from outside the object to which the field belongs.
Mutator method: A method written to modify (mutate) a field in an object.
Cohesion: Something is said to be cohesive if all of its components are tightly related. A method can be said to be cohesive in their own context if they are limited to performing one task.
External Method Call: When an object of a class wants to call a method in an different object, it uses dot notation, by using a "." between the identifier of the object and the name of the method.