

Frontend is what is being actually interacted with by the intended user.
In a car the frontend is:
- Steering wheel
- Gear stick
- Wheels
- Seats
- Pedals
- Lamps
- Ports for pouring in oil, windscreen washer, fuel
- All the different buttons on the dashboard and elsewhere
- Doors
- Keyholes
In a car the backend is:
- Engine
- Gearbox
- Fuel pump
- Cabling
- The actual lightbulbs inside the lamps
- Mechanism for reacting to key being turned in the lock
Etc.
Frontend is what is what is being physically used, backend is what actually makes all of this function. Of course anyone can also go poke at the backend, but without some very deep knowledge, you’re bound to break something. Better let the backend specialists (regarding cars: a mechanic) handle whatever counts as backend if they need to be touched.
In a physical shop the frontend is anything the customer interacts with, while backend includes for example the workers’ pause room, the intermediate storage for goods brought to the store by lorries, etc.

Some literal translations of the books’ names into English. They are unlikely to correspond with the real English titles, but might be enough for guessing what books these are in other languages.
Das ABC der Rollenspiele – The ABC of role playing games
Die göttliche Komödie – The divine comedy
Liegt die Antwort in den Sternen? – Does the answer lay in stars?
Eine kurze Geschicte des Universums – A short story of the universe
Der Außenirdische ist auch nur ein Mensch – Even the extraterrestrial is just a human
Ihr habt keinen Plan - darum machen wir einen – Youse have no plan - that’s why we’ll make one
Kosmologie für Füßgänger – Cosmology for pedestrians
Was hat das Universum mit mir zu tun? – What has the universe got to do with me?
Sieg der Blödigkeit – Victory of stupidity
Unberechenbar – Unreliable
Die Zukunftsformel – The formula for future