A collection of a same kind of entities is known as an Entity Set or entity type.
For the COLLEGE database defines earlier objects of concern are Students, Faculty, Course and departments. The sets of all the students' entities form a entity set STUDENT. Likewise collection of all the courses creates an entity set COURSE.
Entity sets require not be disjoint. For example - an entity may be part of the entity set STUDENT, the entity set FACULTY, and the entity set PERSON.