I can't give you a metaphor on this occasion
(probably could but my brain can't come up with anything)... Are you referring to Chilterns in particular or more generally? If generally there is alot of info in the careers section if you do a search you'll find hundreds of posts that explain the different areas.
Have you applied for Chiltern? It's much the same as most others, written application with CV etc. if selected then assessments through OPC, MMI, then DMI etc... (or in whichever order they fancy). Paper based for GB.