I didn't learn what primary and secondary sources were until way too late in my schooling. So I thought I would do a little review of that here.
The basic principle is: A primary source is something written by the person, at the time of the event. A secondary source is something written by someone who wasn't there, later.
This isn't always black and white but rather a continum. A source that is written by the person but later is a somewhat primary source, but the memory of the person could have changed the story. Or a somewhat secondary source could be written by a person who was close to the person who experienced the story, or, more secondarily, a person who heard things third, fourth or even fifth hand.
So, a quiz. What is a death certificate? answer: some of both. It is a primary source about the person's death, the person filling it out has a close knowledge of the time, place and circumstances of the death. But it is a secondary source on everything else. On my grandmother-in-law's death certificate, her children that helped fill it out didn't know anything about the grandmother's place of birth or parents.
Something else to consider as we are evaluating sources. Especially when we are evaluating two sources against each other.