Lintels are members supporting a wall over window or door openings.
Lintel is a horizontal structural member spanning and usually carrying load above an opening.
Opening may be like the opening of doors and windows. Lintels are provided above the doors and windows to support load of the wall above it.
In case of high rise buildings, the masonry walls are usually not able to withstand their self weight and the slab weight. In such cases, the beams are provided exterior walls at each floor level to support the wall load and perhaps some roof load also. These beams are termed as spandrels.