Wingardium Leviosa is the main spell in the game that is learnt in Year 1 and is used to build Bridges, Staircases and basically any pile of bricks that need to be put together. When it isn't for building, it is for carrying. It can be in normal form and Dark form, and in dark form it is referred to as Dark Magic.
Hermione using Wingardium Leviosa on a banana.