What is a key difference between a class and an instance?

A class serves as the blueprint or template for creating objects, defining the properties and behaviors that those objects will have. This analogy to architectural plans is particularly apt; just as architectural plans provide a detailed outline for constructing a building, a class lays out the structure for creating objects in the program. When a class is instantiated, it generates an actual object based on that blueprint, with its own set of values for the defined properties and the functionality described by the class methods.

Thus, the correct answer effectively captures this relationship, emphasizing that the class defines what an object will be, while the instance is the tangible object created from that definition. This is key to understanding object-oriented programming, where classes allow for the creation of multiple instances, each with individual states but sharing the same structure and behavior as dictated by the class.