Stereopsis

Stereopsis is an appearance of something having physical extent along the axis away from the viewer, being solid and 3D, rather than flat and 2D.

The human perception of stereopsis is formed in large part from binocular disparity.

The term "stereopsis" comes from Ancient Greek stereós meaning 'solid', and ópsis meaning 'appearance' or 'sight'.

It is related to depth perception, but depth perception is vague, and may only mean identifying the distance away of a flat object.

Depth perception due to focal cues is a main component.

Head movement plays a part, such that the human brain likes to see a small perspective shift, which helps.