For the most part the macOS seems to work pretty well. Yes, there are issues now and again, but it just chugs along from day to day doing what it is designed to do. However, occasionally an App will get stuck. You may see the SBBOD (Spinning Beach Ball Of Death) or it will just sit there frozen. When this happens you have to quit the App. This article describes two ways to “Force Quit” an App in macOS Catalina, but it is pretty much the same procedure for all recent versions of the macOS.