Paint Mediums adjust the properties of the acrylic paints they are mixed with. They can change the thickness, drying times, shine and texture of the paint.
Glazes are a thin layer that is very translucent, allowing the colour underneath to show through.
Paint masking fluid help you protect an area of colour when spraying or overpainting. This can then be peeled off to reveal the detail after you are finished.
Paint Varnishes protect the painted surface from grime and wear when handling the figure and also help protect it from dust and UV discolouration over time. Varnish comes in Gloss, Satin and Matte finish. Satin is a middle ground between Gloss and Matte.