The game view is where we run our games. See the unity manual on the Game View.
In the game view we get to see what actually happens in the game when we test it. It shows us what players will ultimately see. It shows us views rendered by cameras in our game.
It’s very important to know that while the game is running, any changes we make will not be saved. At first, this can seem frustrating, but it’s for a good reason: The game is running!
Players playing the game are also making changes to properties (like the position of a main character), and it would be really annoying if we had to move them back to the start of a level after every time we tested it.
Every beginner will start adjusting settings and forget that Unity is “in play mode” (running the game), and then they will lose their changes. It happens to all of us. One way to help prevent this is with a play mode overlay tint.