Question

Explain the difference between a primary source and a secondary source.

Answer 1

A primary source is a document or account created from the time under study.

A secondary sources is a document or account created or written after the time
under study. Usually by people who study in whatever subject that is under study.

Answer 2

A primary source is a document that is written in the time but a secondary source is sources like a textbook. 
The way I remember is a primary source is a thing that was written or done at the time. PRIME-in latin it means 1st
Secondary sources are SECOND and not in the time.