Advanced masking allows you to manage masking on Elementor native widgets.
You can apply masking on the basic widgets available in Elementor free:
Image
Image-box
Video
Several options are supported:
Some default PNGs
Custom PNG File
Custom SVG File (when the option is enabled https://docs.elementor.com/article/587-enable-svg-support-in-elementor)
Default CSS Clip-Path
Image
The PNG images can be managed as backgrounds by adjusting:
Position
Repeat
Size
Clip-Path
By selecting Clip-path your mask is based on CSS functions which generate parametric shapes based on coordinates. Please, take a look at the generator at the following link to help you shed a light on this matter: https://bennettfeely.com/clippy/
Here you are given several predefined shapes.