Shooting line consists of adding additional line to a previous cast.  You may have made a cast, but you see a fish surfacing 5 or 10 feet beyond your fly.  Shooting line gives you a chance to present your fly to this fish before it has time to move from that spot.  With your line hand, strip the additional amount of line you need.  For this example, we’ll go with 5 feet.  Strip 5 feet of line from your “reel” and let it lay on the ground near your feet.  Pinch the line between the reel and your stripping guide.  Make a couple false casts while maintaining your pinch on the line and then make a forward cast and release the fly towards your target.  Pinching the line and timing your release are key to shooting line correctly.