What do you understand by the terms entity, entity types, and entity set in DBMS?

Entity: An entity is a real-world object having attributes, which are nothing but characteristics of that particular object.
 
Entity Type: Entity type is nothing but a collection of entities, having the same attributes. Generally, an entity type refers to one or more related tables in a particular database.
 
Entity Set: An entity set is the collection of all the entities of a particular entity type in a database. For example, a set of employees, a set of companies, and a set of people can come under an entity set.