Start with what the Horch 901 is: a car with gasoline engine, from Horch. What it meant takes a little longer.
The hardware
The engine is gasoline engine. On the scales it comes to 2700 kg. These are manufacturer figures carried by Wikipedia and Wikidata, not road-test measurements.
Family and rivals
Its Horch stablemates include the Horch 853 Voll & Ruhrbeck Sport Cabriolet and the Horch 10.