Operators with undo (Ctrl + z) and without

Defining operators, we most often provide for the ability to undo the action they performed - if after executing the operator the user presses the Ctrl + z key combination, all the effects of the operator on the scene should be canceled. However, in some cases, it may be necessary to define an operator that will be ignored if the user tries to undo its actions. Blender's API allows us to create both types of operators by simply specifying the ability or prohibition of undo in their parameters.

Read more: https://b3d.interplanety.org/en/operators-with-undo-ctrl-z-and-without/