By adding metadata to your files, you are adding extra information to your pages, and that in turn helps your website to gain ranking on the search engines.
All fields, except for keywords, can be edited when the file is used in a content element. But by adding it through the Filelist, it is automatically pushed out to where the file is being used.
To access the file metadata, click the title of the file when you are in the folder. (Img. 3.5.1)
The metadata contains 4 fields.
The "Title" field (1) shows up on the front end when the visitors mouse over the image. It can also be used in the element type "File Links" as the title of a downloadable file, instead of using the file name.
The description (2) is connected to the caption for images. In the case of using a "File Links" element, the description text will appear below the link.
Keywords (3) can be added to the file, comma separated, to enhance search results.
The Alternative text (4) is connected to accessibility of the file, meaning if the image can not be displayed on the front end or is the visitor is visually impaired (having a program read the information for them), this text will be used instead of the image. But it is also a good way to add more information to the page, that the search engines can use. In regular cases, this text is only visible in the HTML code.