Synthetic Sleeping Bags are usually heavier and bulkier than Down Sleeping Bags so more suited to campers not too worried about weight. Great for car camping and those who don't have to carry them on their backs.
Synthetic hollow fibres are used to create loft, and insulated layer and hold warmth in. Synthetic-fill sleeping bags retain warmth when wet and are faster drying than down bags, because moisture gets trapped between synthetic fibers, not inside them. They are also generally less expensive than Down Sleeping bags and Down Quilts.
As with all sleeping bags ensure that you get one suitable for your needs and with temperature ratings right for the conditions you'll be out in.