A semi-automatic washing machine (more commonly known as twin tub in the Philippine market) have two tubs side-by-side - one for washing, the other for drying. You have to manually add water and detergent to a semi-auto, and manually transfer the washed clothes to the dryer tub as well. Meanwhile, a fully automatic washing machine does most of the work for you. Your machine will put water and detergent, and even dry your clothes after the cycle without you having to intervene in the process.