Immersive mode locks your mouse, keyboard, or both to only send messages to the host computer.
Keyboard Immersive Mode
allows you to pass important Windows keys from the client to the host. These include things like alt + tab. If you have immersive mode off, that combination will be sent to the client computer. If immersive mode is on, that combination will be sent to the hosting computer.
Mouse Immersive Mode
Mouse immersive mode locks your mouse into the Parsec host. You cannot leave the Parsec window with your mouse if you have mouse immersive mode on. If the mouse's immersive mode is off, your mouse will not be locked into Parsec. As soon as you click outside the Parsec window on the client computer, all keys and mouse presses will be on the client computer. If you click back into the Parsec client window and your keyboard is in immersive mode, your Windows keys, like ctrl + alt + delete will pass to the hosting computer again.