What is the little box next to the Start Page in Safari’s tab bar on macOS?
Title says it all. See screenshot. I just noticed this today for the first time. Obviously some kind of shortcut for opening a website that seems to always be there. Is it new? It opens the first bookmark in my Favorites but I didn't tell it to do that (i.e., my first bookmark is not set as my home page). Tried Google AI search for "tab bar safari explained macos apple official page" and came up empty. Lots of useless hits, Apple Developer generic tab bars, using Profiles, using tab groups in Apple Vision Pro (I don't even know what that is), etc. Can anybody point me to any documentation? Like what it's called and how you set what website loads? Thank you in advance.
[Edited by Moderator]
Original Title: What the h***k is this little box on the left of the Start Page in the Tabs bar
MacBook Pro 13″, macOS 10.13