Page Layout can be considered a lightweight alternate to Page Manager.
With Page Layout, you can create new pages (or paths, i.e. /about), and put content onto them, by placing blocks - much like the Block Layout page.
Each page can define multiple variants, where each variant can have their own set of conditions when to be selected.
It’s also possible to overwrite existing pages and content types. i.e. node, by defining a page with path `/node/%`.