A section view starts with a cutting plane drawn through the object, indicated on a parent view by a section line (commonly labelled A-A). The section view itself shows the cross-section as it would appear if the part were sliced on that plane and viewed perpendicular to the cut.
Sections expose internal structure that orthographic elevations can't. For a gate, a typical section view shows the wall thickness of the RHS, the way battens fix to the back of the rails, the inside of a lockbox, or the bolt detail at a footplate.
The convention is to fill the cut face with hatching: parallel lines at 45 degrees, rotated for adjacent parts so each member reads as a separate object. CAD60 doesn't generate full section views automatically yet, but planned for future model variants.