Final answer:
In a database system, an entity represents a real-world object, concept, or event for which the database is created, while a schema is the blueprint of the database, and a tuple is a record within a table.
Step-by-step explanation:
Within the context of a database system, an entity corresponds to some part of the real world for which the network is developed, with its data being stored within the database. An entity could represent a physical object, a concept, or an event that is distinguishable within the specific domain of the database.
For example, in a university database system, an entity could be a 'Student' with attributes such as student ID, name, and course of study. These attributes provide more details about the entity and are stored in the database along with it. The term 'Schema', in the given options, is actually the structure or blueprint of the entire database that defines how data is organized and how the relationships among data are associated. A 'Tuple', usually understood in the context of a database, is a row within a table that contains specific data for a single record or entity.