It captures whatever is cropped or framed where the frame has handles that can be dragged to get the aspect of the screen that is desired.
If the tweet spans more than the screen, then it won’t capture what’s off screen, But if the screen size is zoomed out, then yes, it will capture more.
It saves to a Jpg file and can also print to a pdf file.
Jpg images can be uploaded to an image store website for pasting into to a webpage.
Thanks.