[PetitPrince]

I agree the "what it is for" of each layer could be improved. Digging up the wiki [1], there's (I'm aggregating the content of "significance" and "uniqueness"table):

- Standard: "Attempts to do many things at once (Jack of all trades, master of none)"

- CyclOSM: "Contour lines. Cycle map. World coverage"

- Cycle Map: "Contour lines. "Focuses on bicycle features, shows bicycle routes"

- Transport Map: "Displays routes, and public transport. Roads are not most prominent feature."

- ÖPNVKarte: "Displays routes, and public transport. Roads are not most prominent feature."

- Humanitarian: "Focuses on the developing countries with an emphasis on features related to development and humanitarian work. Good contrasting style in terms of overall colour choices. Terrain shading. Many new/different icons (particularly for basic amenities in developing countries) and more nuanced surface track-type rendering. "

[1] https://wiki.openstreetmap.org/wiki/Featured_tile_layers