What is the difference between derived attribute and normal attribute?

A normal attribute is an attribute present in a schema and which has to be entered while entering a tuple.

A derived Attribute is one which can be inferred(derived) from another normal attribute and it need not be a part of a schema.

For e.g.-> In a schema, Date-of-Birth is a normal attribute.While Age is a derived attribute which can be derived from the Date-of-Birth