What is the difference between a blazar and a quasar?
A blazar is a type of quasar that has higher density and can produce much more powerful bursts (gamma rays usually) than a typical quasar.
You have run-of-the-mill AGNs which would be labeled as quasars. If your AGN is spewing out super high energy gamma ray bursts then it is probably a blazar.
Blazars and quasars are both the same thing: active galaxy nuclei. The only difference is that they are oriented at different angles. As SciShow tells us, this means that they can be used to apprise us about different facets of the universe.