This attribute is only used if the href attribute is set.
The download attribute specifies that the target will be downloaded when a user clicks on the hyperlink.
Download attribute is most useful when user click on direct download img, .pdf, .txt, .html type file.
If not include download attribute, then image,. pdf, .Text, .html type file open in browser not direct download, and download for need right click and save as option though download this type file.
<a href="http://localhost/fdold/wp-content/uploads/2015/07/download.jpg" download>