Unfortunately for beginners, this is different for every window manager, and for most window managers, it can be configured in many ways.
"Debian GNU/Linux: Guide to Installation and Usage"
John Goerzen and Ossama Othman
It will have two or more entries that were configured automatically when you installed the system.
"Debian GNU/Linux: Guide to Installation and Usage"
John Goerzen and Ossama Othman
She saw him coming to her over mountains-again and again, she caught a glimpse of him, configured among the peaks, and striding toward her-yet between them was a valley torn with storm....
"She Buildeth Her House"
Will Comfort