A glaze is purely an aesthetic product that contains a very, very light abrasive (Kaolin) to lightly burnish the surface. A glaze provides gloss but very little protection; it's often referred to as Show Glaze because glazes tend to create a "wet-look" (jetting) shine they have come to be used by enthusiasts to maximize shine and gloss on concourse show cars, historic and exotic vehicles.
They are also used on a ‘thin’ clear coat (bear in mind that a clear coat has a thickness of 1.5 – 2.0 Mils, removing more that 0.3 mil (0.0003") of clear coat will cause premature paint film failure) if the clear coat thickness has been reduced by this amount apply a glaze as opposed to using an abrasive polish; risking further clear coat reduction