What does this indicate?

After working with Excel for decades, this is the first time this appeared in a spreadsheet I use often. The contents of some cells are shown in the formula bar inside of an colored, filled oval, with a icon next to it. See below.  I have no idea what this is suppose to mean and why did it suddenly appear? Thanks for insight. Bonus question: how would you go about searching for an answer to this on a search engine? (reverse image search did not work)