base.yaml: The base essential configuration, which contains components for reading the desk height, preset buttons, etc.
stock.yaml: Inherits everything from base.yaml and adds components which are useful on stock firmware, such as the WiFi hotspot, web server, and Improv Serial
debug.yaml: Inherits everything from stock.yaml and adds components which are useful for debugging

Addons

Major parts of the config are separated into "addons" so they can be easily included or excluded. The following addons are available:

presets.yaml: Adds support for recalling and setting presets on the desk control box
runtime-config.yaml: Adds support for runtime configuration options (you might want to remove this if you are configuring everything via ESPHome yaml)
bluetooth-proxy.yaml: Contains the necessary configuration to use the Upsy Desky as a Bluetooth Proxy
stable-ids.yaml: Contains configuration necessary to keep some entity IDs stable via the HTTP API