Updated April 8th, 2020.
The latest Mac OS is 10.15.4 (Catalina), released Tuesday, March 24th, 2020. A supplemental 10.15.4 update was released Wednesday, April 8th, 2020 addressing a FaceTime bug, an Office 365 sign-in bug, and a lot more. The supplemental update is highly recommended. (Remember that upgrading to Catalina from any other macOS is a big deal, and you should be sure that your apps are ready for it.) See this article for information about compatibility with 10.15.