Keys & Attributes specifies

Derived attribute:
An attributes whose values can be derived from the values of related attributes or entities.
E.g- Age could be calculated form birthday.

Primary Key:
An attribute or set of attributes that uniquily identify a pritcular record or a tuple in relation.
E.g-memId is used to identify a student

Foreign Key:
An attribut or set of attributes with in one relation that is a primary key of another relation.

Candidate Key:
Minimal set of attributes used to identify a occurence of an entity type.Can have more than onecandidate key for an entity.

Composite attributes:
Attribute composed of multiple components each with an independent existance.
E.g-Address(street,city,postcode)