Stitching is a way of connecting two pieces of fabric together with loops of thread. The thread is pulled through the fabric with a needle when you are sewing by hand, or done automatically with a sewing machine. A lot of stitches in a row makes a seam. Stitches can be placed to make a pattern, like the embroidery in the picture.
Sometimes when you get a bad cut, your skin will be stitched back together to help it heal.