In Cartesian printers, the extruder is moving along the X axis, Y axis and/or Z axis. Every axes has its own resolution, this is the minimum length that is possible to achieve in that axis and is related with the number of steps that the stepper motors can do.
So, if we trace the solid figure with the minimum volume that the printer can achieve based on its axis resolutions we obtained some sort of a cuboid
The length of the cuboid in X is the resolution of the printer in the X axis, the same logic applies for Y axis and Z axis.
In the figure it is possible to see 27 (3x3x3) cuboids genarated:
if the resolution of the printer in X axis is 0.1 mm, in the Y axis: 0.1 mm and in the Z axis: 0.1 mm, the volume of these cuboids is going to be 0.1 mm x 0.1 mm x 0.1 mm
Now, consider a Delta printer:
What is the solid figure with the minimun volume that can be traced with it?