Pad

A pad is a conducting landing where a part solders, a probe touches, or a bond wire holds on.

Pads are where the drawing meets the real world. Too small, and the iron or the bonder misses. Too large, and solder slumps or a rule fails. A 0805 resistor pad might be 1.0 by 1.2 millimeters of copper with a soldermask opening a little larger. A chip bond pad might be 70 micrometers square of top metal with a passivation cut. On screen the landing is a rectangle or a rounded rectangle with a hole in the mask color, and maybe a drill if it is a through-hole pin.

The landing is a large square. The wire that reaches it is much thinner.

On a board, pads live inside a footprint. On a chip, a pad is often a cell with a pin name. A via-in-pad is a via that shares the landing. The shop must allow it. Silk is ink. The solder sits on copper the mask left open. The part outline that owns those openings is footprints are almost cells. The sheets under the copper are a PCB stackup. A hole that connects two of those sheets is vias and contacts.