Start with what the Mercedes-AMG GT4 is: a car with gasoline engine, from Mercedes-AMG. What it meant takes a little longer.
The hardware
The engine is gasoline engine. On the scales it comes to 1390 kg. These are manufacturer figures carried by Wikipedia and Wikidata, not road-test measurements.
Family and rivals
Its Mercedes-AMG stablemates include the Mercedes-AMG F1 W15 E Performance and the DTM AMG Mercedes C-Coupé.