When it says that a strategy or intervention evidence based what does it mean?

Evidence-based means that the strategy or action is based on the results of a rigourous testing of an idea which can be repeated by anyone with the same equipment and obtain the same result. [also scientific method]. The result from testing is now evidence, or a fact. Action based on the result then relies on fact to guide action.

Action based on faith, dreams, or you saw once that it happened this way is noot based on evidence.