@MisterE Alt (alternative) text is used to describe the image. it's used by screenreaders.
You should use it for any image really, when posting.
On a webpage its good to fill in the alt text if the image is conveying information, relevant to the content on the page. If its just for decoration, filling in the alt text is not required.
@MisterE With difficulty. Especially if an image is a link. Without alt text, a user would have no idea where they were going.
@vozoto Thank you.
@MisterE @Hulio if posting from the web interface, upload the image and then hover over the image with your mouse. You'll see some text saying "Describe for the visually impaired", as well an option to change teh focus for the preview (ie. if its a large image, you choose the part that displays in the feed)
@vozoto Thanks for the explanation.
What if there isn't alt text? How do people use the web?