What is the difference between Alternators and generators?

Generators produce electricity as direct current and Alternators produce electricity as alternating current. As alternators produce electricity more effeciently, and they are smaller and lighter and are used in modern vehicles.
A generator creates direct current in the manufacture of power. An Alternator creates alternating current in the creation of power. Alternators can have diodes installed internally so that they have a D.C. output.