The answer is fairly simple: Nespresso pods work in a very similar way to a traditional espresso in term of their brewing physics.
Coffee contains oils which are extracted into the drink when water passes through the puck of coffee under pressure. This achieve two things: it increases the body of the coffee when compared to filter brewing; it also creates crema as the oils mix with air and create the tiny bubble on top of the drink.
What is different between traditional espresso and a nespresso pod is that the dose and grind size is already set up in the capsule. Baristas check grind setting and dose weight all the time, whereas the Nespresso capsule is a far more stable brewing process.
Here at Roar Gill we love traditional espresso – though it always takes a few shots to dial in the coffee to get it tasting right. The Nespresso technology delivers much more consistency compared to an espresso machine - we love the repeatability of the Nespresso tech. Any barista worth their salt will own up to how espresso changes between shots – coffee pods remove this from the equation.
That said, the style of coffee is fundamentally different. Nespresso pods have a mere 5-5.5g of coffee in each pod, whilst a single espresso could be 15g. Therefore the shot from a pod is always lighter. So do stick to the shot sizes recommended wherever you can!