Tamping
What is tamping in coffee?
Tamping is pressing ground coffee down into a firm, flat, even layer with a tool called a tamper. It is essential for espresso, where an even puck stops water finding weak spots. In a moka pot, though, you should never tamp: the coffee is filled level and left loose.
Uneven tamping is a common cause of channelling in espresso. In a moka pot, tamping packs the coffee too tightly, so pressure builds up and the coffee tastes bitter.