Saying something is primary or secondary is talking about how we came to know that information. Professional genealogists don’t use primary or secondary to refer to sources because one source can contain information that is primary and information that is secondary.
I was the informant for my mother’s obituary. I provided the information. I knew first hand the date and place of her death, where she would be buried, who here husband was, who her children and grandchildren were, and where she had worked. That information I provided was primary information.
The information that I provided about her date and place of birth, when she graduated from college, and when she started work was secondary information. I was not there when those things happened. My knowledge of that information is not first hand–it was something I was told or read on a document or record.
Calling information primary or secondary is not saying it is correct or incorrect. It is simply stating how we came to know the information. Those things in Mom’s life that happened after I was able to remember are things about which I have primary knowledge. Those things in her life that happened before I was born I do not have primary knowledge of.