Matt sheen. No shine or very little shine. However 3 coats of a matt varnish will produce a sheen that is almost the equivalent of a satin.
Satin sheen. Another way to describe satin is eggshell. In other words the sheen level is about the same as the surface of an egg when 1 coat has been applied. 2 coats will be a bit shinier.
Gloss sheen. Very shiny, if you hold an object against a piece of wood that has had 2-3 coats of a gloss varnish applied there will be a clear reflection of that product in the wood.