An article is an agreement between the member states on how the EU will run, the groundrules if you will. For instance Article 288 of the Treaty of the European Union allows for the creation or regulations, directives, opinions and recommendations.
The text of that article also spells out the differences between these things. In fact the language is surprisingly plain but most people will simply never read them for fear of being bogged down in 'legalese'.
A directive is a legal obligation which is imposed on a country, the legal basis for that obligation - the power behind the directive - is the article the countries agreed. A directive tells a country that by a certain date they must have a specific outcome, but unlike a regulation it doesn't tell the country's government how they must get to that point.
Article 288
To exercise the Union's competences, the institutions shall adopt regulations, directives, decisions, recommendations and opinions.
A regulation shall have general application. It shall be binding in its entirety and directly applicable in all Member States.
A directive shall be binding, as to the result to be achieved, upon each Member State to which it is addressed, but shall leave to the national authorities the choice of form and methods.
A decision shall be binding in its entirety upon those to whom it is addressed.
Recommendations and opinions shall have no binding force.