What is alt used for?

Answer 1

alt attribute specifies an alternate text for an image, if the image cannot be displayed. The alt attribute provides alternative information for an image if a user for some reason cannot view it.

Answer 2

And using alt to every images is good practice for seo (search engine optimization) too.

Answer 3

it help to search image smoothly

Answer 4

If any browser fails to display the image then the text will be shown what you had given in alt!! If you keep it blank nothing will be shown!