When playing on a wet grass pitch, mud will prevent conventional boots from gaining enough traction to stop you from sliding around. Enter the so-called SG-soles, which stands for "Soft Ground" - ie wet surfaces. Football Boots for wet surfaces are typically equipped with fewer, longer screw studs than we normally see on other shoes.
This means that they dig further into the ground, and thus ensures the necessary grip you need, and that mud and grass are less able to accumulate under the boot. There are also SG-boots, combining the long screw studs with the shorter plastic blades that we know from boots for AG, designed to give you the optimum configuration of studs for enhanced grip in the wet ground.
Remember, football boots with SG-sole are designed specifically for wet, soft grass surfaces, so they can not be recommended on regular, permanent grass or artificial turf, as they will cause damage to the surface and injury.