Status bar > Keyboard Shortcut Override Toggle
The Keyboard Shortcut Override Toggle lets you toggle between using only the "Main User Interface" shortcut keys and using both the main shortcuts and shortcut keys for functional areas such as Editable Meshes, Track View, and so on.
When the Override toggle is off, only the Main User Interface shortcuts are recognized. When Override is on, both main UI and functional area shortcuts are recognized; however, if there is a conflict between a shortcut assigned to a feature and one assigned to the main UI, when Override is on, the feature's shortcut takes precedence.
You can customize keyboard shortcuts by using the Keyboard panel of the Customize User Interface dialog. The lists in the keyboard panel show which shortcuts have been assigned to which command or feature.
See also