Why it matters in the cup.
Coffee glossary
Puck
Before the water hits
What it means
The compacted bed of ground coffee inside the basket. Everything about espresso depends on how the puck resists water — its density, evenness, and integrity govern flow and extraction quality. A cracked, uneven, or poorly formed puck gives water weak paths to exploit, and the espresso loses balance as a result.
Keep going
Where this leads
Each one pushes this into the cup, compares it, or helps you act on it.
Before the water hits
Distribution
Start with how the bed is built.
Level the coffee deliberately before tamping.
How the basket changes things
Headspace
Then make sure the basket gives the puck room to brew correctly.
Match dose to basket size so the puck sits where the machine expects it to.
How the shot starts
Pre-infusion
The first seconds decide how the puck behaves under pressure.
Use pre-infusion to smooth the beginning of the shot, not to compensate for careless preparation.
What people mean when they say "extraction"
Espresso Extraction
Everything about the puck only matters because it changes extraction.
Separate extraction from strength in your thinking. One asks how much was dissolved, the other how concentrated the drink feels.