I've attached a picture of what a cross section would look like in different figures. A cross section is the shape made when a plane cuts through a solid.
The cross section of a rectangular prism; parallel to the base would be a rectangle and perpendicular to the base would also be a rectangle.
Cross sections parallel to the base take the shape of the [tex] \boxed {base} [/tex].
Cross sections perpendicular to the base take the shape of the [tex] \boxed {lateral~ face} [/tex].
Cross sections at a diagonal to the base make a[tex] \boxed {stretched~out~base} [/tex].
