This article is introducing terms to describe chainmail.
The classic pattern of medieval chainmail is called European4in1. It has four rings linked into each ring. The pattern has different properties if it is turned by 90 degrees. Usually, the torso of a chainmail shirt is made in a way that lets the hanging mail contract (closed-hang). That way the mail can swing sideways and absorb energy when hit.
The European4in1 pattern has a structure like a grid with rows and columns. In closed-hang orientation, rows run horizontally. Inbetween rows there is a line of rings facing the other way. Inbetween columns there is nothing like that. That is how to tell them apart. In schematic depictions, the line between rows is typically not shown.