Standard keyboard shortcuts can normally only be used when the application window has focus. System-wide hot-keys, on the other hand, can be used when you are working in another application, or even when the application is minimized.
Note: System-wide hot-keys take precedence over standard keyboard shortcuts. In other words, if a key is configured as both a standard keyboard shortcut and a system-wide hot-key, then only the hot-key command will be run when the key is pressed.
Open the Options dialog and click on the Hot-Keys tab to see the System-Wide Hot-Key Assignment list showing the currently configured hot-keys and which commands they are mapped to. If the list is empty, you will need to add hot-key assignments. From the Hot-Keys tab of Options you can:
From the Add and Change dialogs you can assign a hot-key and which command it will be mapped to.
Press the key or key combination that you want to use as the hot-key. When you release the keys, the Press Key dialog will close and you will see the keys you pressed on the Add or Change Hot-Key Command dialog. Note that the keys you press can be used in conjunction with the modifier keys Shift and / or Ctrl and Alt.