@Schwabstrasse Both. Lens <-> workpiece distance is a matter of choice. The closer you get, the smaller the focused spot becomes, and can engrave much finer details, but, you lose focus depth (you won't be able to cut through materials that you could before).
Example (numbers are not exact):
70mm distance: spot size = 0.15mm, can cut 6mm thick material
30mm distance: spot size = 0.05mm, can cut 2mm thick material
There are special lenses that break this rule but for the ones we use it works this way. It's a long topic and we're already off-topic, might need to make a new thread.