A verandah is an outdoor porch with a roof. Most verandahs extend along the sides and front of a house or building. It’s usually spelled "veranda," but spell it with the h if you’re in a Jane Austen novel. Verandah.
In the US, veranda (without the “h”) is been standard since the 1850s, but British English kept the “h” for about 100 more years. These days veranda is more common everywhere. It comes from the Hindi varanda, and the porch style was copied from India by the English. The word's origin goes back to the even older Portuguese word of the same name.