An entity type usually has an attribute whose values are distinct for every individual entity in the collection. Such an attribute is known as a key attribute and its values can be used to recognize each entity uniquely.
Strong entity set: The entity types having a key attribute are known as strong entity types or regular entity types.
Let us first answer the question:
What is an attribute?
An attribute is a property used to define the specific feature of the entity. So to define an entity entirely, a set of attributes is used.
For example, a student entity may be defined by the student's name, address, age, course, etc.
An entity will have a value for every of its attributes. For example for a specific student the following values can be assigned:
Address: B-4, Mayapuri, Delhi. Course: B.Sc. (H)