How are the wavy/curvy images (often w/ illustrations) in many modern experiences created? (example provided) [closed]

This is what I'm talking about:

First of all, what do you even call this type of design?

Specifically, how are the curved lines accomplished? I've gotten close in Affinity Designer inverting a freehand selection, but it never comes out right.

For the web I'd think that you'd ideally want to use svg/css, but that's a whole other can of worms, and for what I'm doing I need an image.