You definitely have seen baristas pressing that coffee with their tamps before they make you a delicious cup of coffee? It is also important when using Nespresso reusable pods.

The main purpose of it is to evenly distribute the coffee in the pod as well as compress the grinds to have no air pockets. The secret of brewing good coffee is all about passing hot water through coffee grinds to extract the oils of the coffee grinds completely. 

The more fine the coffee, the less pressure applied - if the fine ground is tamped too much the water will not go through the coffee pod.

If you didn't buy the tamper, please press the coffee into your coffee pod with the bottom of the scoop that came with it.