Is there a common name for this kind of transition? This is a bit like a Slide Transition, but the content does not move here. (The animation looks jerky because of low FPS of the gif image. It's actually smooth.
In general this sort of transition is called a wipe. I might call it a "layered horizontal wipe". It's generally done by layering two images and then animating a clip path that's applied to the top image. Or you could fix the top image (so that it doesn't resize its dimensions) and animate its width.
It made me think of a lot of the transitions in Star Wars movies.