This image has Alt Text set in the Media Library:
This image has Alt Text set in the Page editor. Click on the image, select the pencil option, then Alt Text. The original Alt Text from the Media Library has been overridden by the Page Editor Alt Text setting for the purposes of this page, but the “default” Alt Text remains unchanged at Media Library level:
This image has Title Text, set in the Media Library. It is used by WordPress for searching images. It does NOT appear in the page HTML, and the screen reader just says “Link”:
This image has Image Title Attribute. This is set in the Page Editor. Click on the image, select the pencil option, then Advanced Options and Image Title Attribute. It is the only one that shows text on mouseover/hover, but the screen reader just says “Link”: