Although not a video, this useful tutorial clearly explains the difference between primary and secondary sources. It even has a short quiz at the end to test your understanding!
Primary and Secondary Sources IRIS Tutorial from Highline College Library
How to Determine if Your Sources are Primary, Secondary, or Tertiary (Penn Libraries, University of Pennsylvania)
Learn the difference between primary and secondary sources from this short 4 minute video tutorial produced by the Hartness Library. Produced in 2012.