Resolved Explain: "Helix 3 is developed with LESS. When customize your site, we suggest you to work with LESS files. All your changes in the LESS files will be compiled into the final CSS files. It will override previus changes."

Is anyone able to explain the following tooltip in the Advanced Tab in Helix3 template admin? It is very ambiguous, and isn't clear if what happens when I click On or Off. Should I turn it On when customising or Off? Should I turn in On when I go live, or Off? Will I lose customisations if I toggle it? Is there a way to undo if I mess it up?

Thanks,
Geoff