Regulations are of general application, binding in their entirety and directly applicable. They must be complied with fully by those to whom they apply (private persons, Member States, Union institutions). Regulations are directly applicable in all the Member States as soon as they enter into force (on the date stipulated or, failing this, on the twentieth day following their publication in the Official Journal of the European Union) and do not need to be transposed into national law.
They are designed to ensure the uniform application of Union law in all the Member States. Regulations supersede national laws incompatible with their substantive provisions. (Source: http://www.europarl.europa.eu/atyourservice/en/displayFtu.html?ftuId=FTU_1.2.1.html)