If you come to garments from quilting, there are a few things you need to know about finishing seams.  If a garment is going to be washed and there are exposed raw edges, these raw edges need to be finished in some way.  I grew up with a good pair of pinking shears for finishing raw edges - in fact, we cut out unlined garments with pinking shears to save a step in construction.  However, loosely woven fabrics such as rayon and many cottons will still unravel in the wash.  Further finishing like a 3-step zigzag or narrow turned and stitched edges may be necessary.