I'm only a recent MacOS user after not using it for over 20 years, so please people correct me if I'm wrong.
But in the end the biggest thing to remember is in MacOS a window is not the application. In Windows or in many Linux desktop apps, when you close the last or root window you've exited the application. This isn't true in MacOS, applications can continue running even if they don't currently display any windows. That's why there's the dot at the bottom under the launcher and why you can alt+tab to them still. If you alt+tab to an app without a window the menu bar changes to that app's menu bar.
I remember back to my elementary school computer lab with the teacher reminding me "be sure to actually quit the application in the menu bar before going to the next lesson, do not just close" especially due to the memory limitations at the time.
I've found once I really got that model of how applications really work in MacOS it made a good bit more sense why the behaviors are the way they are.
But in the end the biggest thing to remember is in MacOS a window is not the application. In Windows or in many Linux desktop apps, when you close the last or root window you've exited the application. This isn't true in MacOS, applications can continue running even if they don't currently display any windows. That's why there's the dot at the bottom under the launcher and why you can alt+tab to them still. If you alt+tab to an app without a window the menu bar changes to that app's menu bar.
I remember back to my elementary school computer lab with the teacher reminding me "be sure to actually quit the application in the menu bar before going to the next lesson, do not just close" especially due to the memory limitations at the time.
I've found once I really got that model of how applications really work in MacOS it made a good bit more sense why the behaviors are the way they are.