It was designed to roughly emulate the espresso machines of Italian coffee bars, in a small and simple device which could be used in any home.
A true espresso requires at least 9 bars of pressure. While the moka pot manages only around 2-3 bars of pressure.
The resulting coffee is thick, strong, murky. If you are using coffee roasted dark, the Italian way, it can be rather bitter if taken black. Personally, though, I love it so if you have never tried it give it a go.