The enormous weight of an armored tank has to be carried by its running gear so that it doesn’t sink or become mired on soft ground. Track spreads the weight of the tank more evenly than tires do - so that there is less pressure per square inch in contact with the earth. In old WWII movies of the Eastern Front - what do you see getting stuck in the Russian mud? Trucks! What is it that can pull the trucks out of the mud? Tracked vehicles!