what's the precise name of command, 'shift + r'? Today, when I study blender with You tube video, I saw the hotkey 'shift+r', which seems to redo last action.

I want to know precise command name of it in case of forgetting that hot key.

If I know the precise name of it, i would find it with 'space bar'(what's the command name of this?).
The option is 'Repeat Last'. You can view and edit the shortcuts in the 'Input' section of the Blender Preferences.