This is a bulb type enema syringe. It is filled and used in the same way that one uses and ear syringe to clean the wax out of your ears.
You fill it by squeezing the air out of it, placing the tip under the surface of a container holding the solution and release the bulb. The syringe fills with the solution.
The enema is administered by inserting the tip into the rectum and squeezing the solution into the bowels. Often individuals will squeeze a few (2-5) bulbs worth of solution into the bowels before they evacuate.
Bulb syringes are usually chosen by people that use an enema as a way to overcome constipation. Overcoming constipation usually only requires a small amount of solution and a bulb style enema syringe can provide it quickly and easily.
People that want larger enemas may be unhappy trying to refill a bulb syringe and may also be dissatisfied with air that is injected along with the enema solution.
You can find this enema syringe here