An LCD hood helps minimize the glare on a digital camera LCD monitor. The hood shields the monitor from bright overhead light and from light coming from the side, making it easier to view the LCD to change menu options and compose shots.
Some hoods come with built in magnifiers that enlarge the image on the LCD for improved viewing. It blocks light and reflections and the small lens allows you to focus on the screen at a close distance. It is an excellent solution for confirming focus or exposure especially if you work out doors a great deal.
Unless you buy an LCD hood made for a specific model, universal LCD hoods attach to digital cameras by Velcro, an elastic strap or by attaching it to a tripod thread. Many fold flat for easy carrying and storage in a pocket or camera bag.
When in the closed position, a LCD cap provides excellent protection for the LCD. The hood does add some bulk and weight to a camera, but it may be well worth it for the the protection it affords.
Tip: Whether you use an LCD hood or not, keep the monitor clean at all times. Smudges and fingerprints make viewing an image on the screen much more difficult to see.