Many stove-top espresso makers on the market have an hourglass shape, but we can find them in a variety of other styles.
Here is a bit more detailed the magic behind the Moka pot.
The pot is divided into 3 chambers: the lower chamber is for boiling the water, the middle one is for coffee grounds, and the top chamber is for collecting the brewed coffee.
The brewing priciple is this:
Water is warmed up in the lower chamber of the pot.
The steam pressure drives the water up through the ground coffee and the filter,
And after that eventually gets collected in the upper chamber as brewed coffee.