What is the difference between "primary information" and "secondary information", specifically as it applies to genealogy research using a library's resources?
I'm operating on the assumption that you mean "primary sources" and "secondary sources."
Primary sources are those which are original information, such as artifacts, documents, etc. that were created with direct knowledge of a situation, often under created during the time under study. This can include things like census data, immigration records, birth certificates, etc. Secondary sources cite or comment on primary sources, but this distiniction isn't always hard and fast.