Since Brexit, the EU law terms ‘direct effect’ and ‘direct applicability’ have at times been conflated. However, they have distinct meanings which should be clarified.
Direct effect refers to the ability of EU Member State nationals to enforce rights derived from EU legislation directly in national courts. In other words, if a provision of an EU Treaty, Regulation, or Directive satisfies the requirements to be directly effective, national courts must enforce the rights that such a provision grants. Therefore, there is no need for nationals to go to the Court of Justice of the European Union (CJEU) to plead their cases.
Direct applicability, on the other hand, refers to whether a piece of EU legislation becomes part of a Member State’s national law without the need for any implementing legislation. EU Treaties and Regulations are directly applicable, as they come into force without any action on the part of Member States. Contrastingly, EU Directives are not directly applicable, as Member States must implement national legislation, before a prescribed deadline, in order to give effect to them.
I didn't grasp Antonio Racano's article.