A good microservice should encapsulate a bounded context. A bounded context is a concept that comes from Domain-Driven Design (or DDD). In DDD, the components of an application are organized around the various contexts or domains in which your software can be interpreted.
As software gets larger, it becomes harder and harder to describe it with a unified model. Your software might serve three different departments in your company that each have their own definition for what a product is, or it might be used by two different types of customers. Describing all of these situations in a unified model is confusing and