A spirit level is a tool used to determine whether a surface is horizontal (level) or vertical (plumb). It typically consists of a sealed glass tube filled with liquid and an air bubble. When the bubble is centered between two marked lines, the surface is level. Spirit levels are commonly used in construction, carpentry, and various DIY projects. There are different types of spirit levels, including bubble levels, digital levels, and laser levels. Each type serves the same basic purpose but may offer additional features for increased accuracy or ease of use. Spirit levels are essential for ensuring proper alignment in various applications.