Plans, elevations and sections are drawings that are 2-dimensional. However, architecture is 3-dimensional.

Perspective drawing

Perspective line drawing
Matthew Lloyds Architects LLP, New Heart for Bow Project at St Pauls’ Old Ford, London, 2004

Architects need to think about what their building will look like when it is finished, so they make 3-D drawings and models of their buildings.

Perspective drawings are a type of 3-D drawing.