Choose Production or Draft to render the scene using the current production or draft render settings without displaying the Render Scene dialog.
You can assign different renderers to the Draft and Production sides in the Rendering page of the File/Preferences dialog. To use the Production and Draft options as a quick way to switch renderers while using identical parameters, assign the two different renderers, set up all your parameters in the Draft side, and then click the Copy Draft Parameters to copy the settings to the Production side.
The only settings that are the same between Production and Draft are the Output Size preset buttons. You can have Production set for OmniMAX 360x360 and Draft set to Custom 320x240, but if you change one of the buttons to a custom setting, such as Custom 1000x1200, that specific button will be identical for both the Production and Draft settings.