ALT and TITLE as descriptive elements
Because visually impaired users are often unable to see pictures, they rely heavily on the description associated with them. ALT tag for images and TITLE tag for other elements have become increasingly important in order to fully describe all elements of a web page.
Not everyone using a computer has vision or hands.
In the event that the user can’t view the image—perhaps because he or she is accessing your page over a very slow connection, because an incorrect src attribute has been defined, or because the user is visually impaired and is accessing the content using a screen reader—the alt attribute provides alternative content that can be displayed instead of the image.