What is the difference between four wheel high and low?

Four wheel drive high is used for everyday purposes such as driving on a snow packed road or light off roading. Four wheel drive low is for special circumstances such as getting out of deep mud and snow or towing a trailer up a steep hill. Four wheel drive should never be used on bare, dry pavement. Use two wheel drive in this circumstance. You will completely ruin your transfer case by using four wheel drive on pavement.