Unlike a primary source, a secondary source can be:

Unlike a primary source, a secondary source can be made or written by an educated person (someone who knows a lot about the subject) or trained expert, but in order to be categorized as a primary soruce, the source has to be directly involved and/ or have existed when the event/occurence is happening. Secondary source could be anything as long as it related to the event being written about. 

Hope this helps!