Taschenkaffeewaage

When brewing espresso you are constantly adjusting your variables to dial in your coffee. The coffee to water ratio is one of these variable.

Generally an espresso has a 1:2 Ratio but this isn't always the case and sometimes the word 'espresso' acts more as an umbrella term for coffees that are outside of this ratio.
A Lungo has a 1:3 ratio and a ristretto has a 1:1 ratio of coffee to water.

Brewing espresso at different water temperatures will change how your coffee is extracted and the overall taste of your espresso.
Using a hotter water temperature will increased the body and sweetness but will have a greater chance of astringency and bitterness, while cooler water temperature will reduce bitterness, body and sweetness and can resulting in a sour, brighter espresso.

Pressure is a critical factor in brewing espresso, typically measured in bars. The most common pressure for extracting espresso is around 9 bars. Proper pressure ensures optimal extraction, balancing the flavours and aromas.

Adjusting your pressure throughout the one extraction is known as pressure profiling and is an entire rabbit hole in itself.

Grinding your coffee right before you brew will drastically improve the taste of your coffee. The reason for this is that once you grind your coffee it has a much larger surface area and straight away starts to loose it's freshness.