Team shape is the most-discussed concept in modern football and the least precisely defined. This page gives a coach a small, working definition of shape they can apply from the touchline, in real time, without metrics or software, and explains how that same reading scales when you do have analysis tools available.
The working definition has three numbers and one rule. The numbers are vertical distance, horizontal distance, and ball-side compactness. The rule is that all three move together. If only one moves, the team is breaking shape. The full guide is in the deep-dive Team Shape Analysis page; this resource is the on-pitch primer.