Espressos require a multitude of tools to achieve the perfect brew. One of those tools is the tamper, as the name says, it just tamps the coffee. The espresso grounds contained inside the portafilter basket need perfect pressure to create that silky coffee with the thick crema. To do this, one needs to tamp the grounds hard enough to create resistance for the water but not too hard where the water can't pass or too soft where the water just goes right through. While it's one of the hardest parts to master, it's where one can perfect the espresso.
