It's an unraveled sweater or any other knitted garment. They yarn is usually just fine, but the balls are small so there will be lots of joins. If they post the size of the sweater it came from, figure you can only make another sweater one size smaller or less.
FYI, you can go to consignment shops, thrift stores and garage sales looking for sweaters. If you find an old cashmere or angora sweater, snatch it up and recycle the yarn!