What is an entity? An attribute?

Entity - A single object that is unique in real world that is under observation.

Attribute - These are the trait or characteristics of the entity type which describes the entity.

Explanation:

An entity is a single object that is unique that is present in the real world and it under observation. For example: - an organization, single person, single product.

An attribute is the traits or the characteristics of an entity type which describes the entity for example the organization entity type has it's name as attribute.