The Invisibility Cloak is a cloak which turns the wearer completely invisible. Harry gets it as a Christmas present from Albus Dumbledore, who had it in his possession since shortly before it's previous owner died. This previous owner was Harry's father, James Potter. Harry frequently used his cloak to explore Hogwarts at night.
The Invisibility Cloak is a shiny, silvery robe – smoother than silk and extremely light. The cloak turns its wearer invisible.
Harry owns an Invisibility Cloak; it is a family heirloom which he is given for Christmas during his first year. He uses it mostly to explore the castle after hours.
Harry has an Invisibility Cloak, which he inherited from his father. It is a shining, silvery robe – smoother than silk and extremely light, and Harry uses it mostly to explore the castle after hours.
Harry and Ron use the cloak to sneak down to Hagrid's after Hermione is attacked to ask him what he knows about the Chamber of Secrets.
The Invisibility Cloak is not completely impermeable. Alastor Moody's magical eye is able to see Harry when he is wearing the Cloak in the Three Broomsticks pub in Hogsmeade.
According to some, a true Invisibility Cloak is one of the Deathly Hallows. United with the Elder Wand and the Resurrection Stone, its owner would become the master of Death.