The stitches in your fabric will pucker if there is too much tension in the seam thread. It is a dead give-away that the crafter did not sew the seams properly. A zig-zag stitch is a side to side stitch used for decorative sewing, stretch fabrics, and seam finishing. You can adjust it by changing the settings on your machine. The higher the number on your stitch length, the longer your zig-zag stitch will be. The width dial indicates and changes the width of your stitch. Zig-zag stitches also protect the raw edges of your fabric by preventing them from unraveling. You can create this type of stitches by hand or with a sewing machine. But it is more convenient and quicker you complete a zigzag stitch with a needle and thread if you are hand sewing a small repair.