What the "protection level" is?

I had to put a variable (the variable name was game over) of one script (whose name was gamecontroller) into another (whose name was player). I watched a tutorial where it told me to write
GameController.Gameover = true, but when I went back to Unity it said: ‘GameController.gameover’ is inaccessible due to its protection level. What does that mean? How could I solve that?

Usually it means one class (script) is expecting to access another class variable but it cannot because it is not public.

ty :slight_smile: