Since 10.4.27, WSN has three configuration modes. You start off in standard mode. If there are certain settings you want to change every time you take your site offline for development or debugging, you can use development mode for that. If there are certain settings you want to change when you're ready to put the site into its' mature long term ideal state, you can use production mode for that.

The effects of development or production mode are defined by you, at Admin -> Settings -> Development Mode and Admin -> Settings -> Production Mode. In general, you'll want to apply minification/caching/speed options in production and apply things that make debugging easier or prevent users from recieving notifications of test data in development. If there's a particular option you'd like to have configurable for development/production which isn't there yet, please contact support to ask about it.

At the regular locations of each setting, you'll see a warning to the right telling you that the setting is overriden in development or production mode. When you see the warning, be aware that the change you're applying is only a change to standard mode. If development and production are set to use the standard value, then WSN won't show you the warning.

To switch your site between modes, simply click the desired mode on the front page of your admin panel.