What do these Numbers actually mean?

One hundred years ago was the modern number plan for German steam locomotives introduced, sorting them by "Baureihen" like 01, but also like 18.4-5 or 55.25-56,58. So, what do these numbers actually mean, and how are they chosen? All models in this video were created and rendered by myself using Blender. Support my work by becoming a channel member:    / @steelbridgemodels   Or by getting wallpaper from my videos: https://steelbridgemodels.gumroad.com/ Follow me also on Instagram:   / steelbridgemodels   Chapters: 00:00 Intro 00:18 Backstory 01:28 Tender Locomotives 05:21 Four Digits 07:39 Tank Locomotives 10:44 Outro DB Class 10 (2007) by Henning Pietsch sourced from: https://commons.wikimedia.org/wiki/Fi... WP 60 001 ex LBE 1 (1936) by Werner Hubert sourced from: https://commons.wikimedia.org/wiki/Fi...