Each part of every Eurocode has a National Annex (NA), unique to the country where the structure is to be built. The NAs will contain the same basic information. For example, they must contain information on the values/methods to be used where national choice is allowed in the main text of the Eurocode. Areas where national choice is allowed are collectively called Nationally Determined Parameter (NDPs) and include such items as load factors, loads, and methods for calculating certain loads, partial safety factors and advice where a choice in a design approach is allowed.
In addition the National Annex can refer to Non-contradictory, Complementary Information (NCCI) which, as the name suggests, is information that supports the use of the Eurocodes with useful guidance not given in the Eurocodes themselves. What can and cannot be included as NCCI is still the subject of much debate but it may include references to some of the material contained in national standards and guidance documents.