The term comes from the days of vector photo plotters, where film was exposed by shining light through apertures arrayed around the edge of a disk (or “aperture wheel”). Each aperture corresponded to a different D code in the Gerber data. Today, photoplotters use lasers to expose the film but the term “aperture” persists and describes the shape and size of the tool used to create a pad or track.
General fabrication process of single and double sided PCBs:
Drilling -> Photolithography -> Etching -> Plating -> Solder mask -> HAL or gold plating -> Milling, scoring -> Testing -> Final inspection -> Packaging and dispatch.
A hole to provide electrical connections between conductive patterns at the levels of a printed circuit board and installation of THT components.