Energy gels are useful for giving yourself an energy boost on your ride. Usually containing high amounts of carbohydrate; they are perfect for slipping into your jersey pocket to take with you on long or short rides.
They should not be taken on longer rides as a substitute for propoer nutrition, as slow release energy will be much more beneficial on these rides; however the gels are useful for giving yourself a boost.
Easy to Use
The gels don't contain a lot of gel, usually only around 25g which makes them really easy to take on quickly, without having to ride with them in your hand.
They have an easy to open top which can be torn with the teeth or fingers making them easy to open whilst riding, then they can be consumed with a single squeeze - perfect for preparing to attack your club mates on a climb.