The main variables in a shot of espresso are the "size" and "length".
This terminology is standardized, but the precise sizes and proportions vary substantially.

Cafés may have a standardized shot (size and length), such as "triple ristretto", only varying the number of shots in espresso-based drinks such as lattes, but not changing the extraction – changing between a double and a triple requires changing the filter basket size, while changing between ristretto, normale, and lungo may require changing the grind, which is less easily accommodated in a busy café.
The main variables in a shot of espresso are the "size" and "length". This terminology is standardized, but the precise sizes and proportions vary substantially.
Cafés may have a standardized shot (size and length), such as "triple ristretto", only varying the number of shots in espresso-based drinks such as lattes, but not changing the extraction – changing between a double and a triple requires changing the filter basket size, while changing between ristretto, normale, and lungo may require changing the grind, which is less easily accommodated in a busy café.
Espresso