It's a font manager that plugs into Photoshop, Illustrator, InDesign and the rest of the Adobe suite...you add/organize your fonts inside of it and it will auto update and allow you to use those fonts in real time even when the apps are open. There should be a trial version give it a shot, but I think its totally worth buying. It will also give you a popup and help you load the fonts if its missing from your system (ie if you're getting files from other designers) and auto update it when its loaded etc.
I've been a designer for 15+ years and we used to use FontExplorer but that was discontinued so I switched to RightFont and it's been very good. It has enough features to make it worthwhile to own. FontExplorer was better but there's nothing like that out there afaik.
I use very custom fonts from rare foundaries that are not in the Adobe Font Library, so I use this tool whenever I do that. You can still use Adobe Font Library.