I think it’s probably useful to mention the Filesystem Hierarchy Standard (FHS) here which describes most of the tree structure detailed in the diagram.
The directory layout mostly adopted by most distros evolved over time though, with major differences existing in how distros view usage of different parts of the filesystem, making it more of a standard that documents how the filesystem is laid out rather than one that defines it.
On a personal note, I hated /run for the longest time, thinking it a pointless, redundant quirk that exacerbated inconsistencies across distros. More recently though, I’ve come to value a space that is now (mostly) implemented consistently as a tmpfs mount from which to handle runtime data.