Shield Charm

The Shield Charm is a spell with an incantation called Protego.

This spell creates a magical barrier that will deflect hexes thrown at the caster.

Harry Potter learned this spell in his preparations for the THird Task of the Triwizard Tournament.

Harry used the Charm to defend himself against Snape's Legilimency during Occlumency training and found himself unexpectedly seeing some of Snape's memories.

Harry used this spell to defend himself and stop various Death Eaters from Summoning the Prophesy away from him during the Battle of the Department of Mysteries.

According to the Weasley twins, many adult wizards cannot cast this spell properly, as they used Shield clothing line.