Can anyone tell me what the icon at the lower right corner of the Quicktime screen is?

Its the Live Text button.

It can identify and let you copy text from videos and photos.

When you see text in the video, pause it, and click on the Live Text icon and it ill highlight any text it can idenitfy. Move your mouse to where the text is. It should turn into a 𝐈 (text select icon) and you can click and drag to highlight the text. You can then hit the command+c keys to copy the text and paste it anywhere you want.

It works wit text in pretty much any orientation, surprisingly well.

I've not noticed that in the past, but I just did a very short (12 sec) screen recording. I opened it and hovered to the bottom corner and I saw that icon. so I pressed it and it highlighted all of the text seen in the screenshot. so I'm guessing it has something to do with the clipboard and saving text to it.

if I'm mistaken, maybe someone else here can clue us in. :)

thanks Phil0124. I thought that might be the case, although I didn't know how to explain it to the OP.

You're welcome.