mud + snow.
they have quite an open agressive block like tread pattern. the tread tends to have excelent self cleaning ablity and they will bite into soft surfaces. the downside is they tend not to have rain grooves in them so will aquaplane easyer than a normal road tyer really agressive ones will hum at speed on the road, there dry grip is not the best ether. but as name says they work really well on muddy and snow cover roads