Pin

A pin is a marked place on the edge or face of a named drawing where a connection is allowed to enter.

A cell without pins is a sealed box. Routers, LVS, and the people who read the cell need a name and a shape: A on metal 1, Y on metal 2, vss on a pad. The pin shape is often a rectangle on a layer the process treats as legal access. Miss the mark and a wire lands on blockage. On the boundary the pin is a labeled box, or a line in a list such as PIN A LAYER M1 (0.00 0.20) (0.14 0.34). A standard cell might be 0.56 micrometers tall with pins on a 0.14 micrometer track.

The square sits on the edge of the block, the place a connection is allowed to enter.

A pin belongs to a net. On a board, the cousin is a pad in a footprint. LEF files publish pin boxes so a digital tool can place and route without opening the transistors. Text painted on the cell is for people. A pin needs geometry the extractor will see. How that name is supposed to match the schematic is LVS: layout versus schematic. The drawing the pin belongs to is cells and instances. The cut that ties the pin's metal to the device is vias and contacts.