What would you like to understand?

When a third vector pokes out of the plane at an angle, scaling it allows the entire 2D sheet to slide up and down through space. With three freely varying scalars ($a\vec{v} + b\vec{w} + c\vec{u}$), the span now encompasses every conceivable point in the 3D volume.

Conditions: The first two vectors span a plane in 3D space.; The third vector is not on that plane (it pokes out at an angle).; The scalars $a$, $b$, and $c$ vary freely.

When a third vector pokes out of the plane at an angle, scaling it allows the entire 2D sheet to slide up and down through space. With three freely varying scalars ($a\vec{v} + b\vec{w} + c\vec{u}$), the span now encompasses every conceivable point in the 3D volume.

Conditions: The first two vectors span a plane in 3D space.; The third vector is not on that plane (it pokes out at an angle).; The scalars $a$, $b$, and $c$ vary freely.