Blazars are just quasars with the jets pointed towards us. Quasars are basically galaxies with active super massive black hole in its centre. Luckily for us, our galaxy has a quiet black hole (quiet meaning it's not feeding like crazy). This picture might help https://ned.ipac.caltech.edu/level5/March04/Torres/Figures/f...

BL Lac in the picture is a blazar. So same object is classed differently depending on is orientation with respect to us.