Usually people prefer to read their books in a certain format. Some like regular print books, some like Large Print and some like to listen to their books or download them in eBook format.
When you know what the icons stand for it can make your search go faster. Also, if you hover your mouse over the icons it will show you the format as well.
Additionally, for items that are in Overdrive, RBDigital or Hoopla a web link will be present.
Here is a quick video that highlights the icons and web link.