Crosswalks are not necessarily marked. For many jurisdictions they exist at the corners of every road intersection.

The question of what a crosswalk is can be surprisingly contentious despite attempts at federal standards! In my city there is a situation where the police department and the transportation department currently define "crosswalk" differently, leading to some rather bizarre situations with police reports and attribution of fault (e.g. pedestrian crossing in something the transportation department considers to be a crosswalk but the police department does not, such as a marked bicycle crossing, because their definition is stricter).

Off topic: imgur showed me the image, then gave me a cookie popup and when I clicked decline, the image was replaced by the text “could not find image”

The GP poster knows what a pedestrian crossing is, what it's for, and how it looks in most countries that can afford to build them; they were just pointing out that the word “crosswalk” is only found in American English.