@StroomAfwaarts @kropot The question mark separates the URL from the parameters. Ampersand separates the parameters from each other.

In the first URL, the tracking junk was the only parameter, so everything can be removed. In the second, it's leaving behind the time code parameter.

On links to youtube.com (as opposed to youtu.be) the video ID is itself a parameter /watch?v=etc, so you'd always be leaving the question mark.