What is the legalization of documents?
Legalization of documents is the certification of the authenticity and veracity of the document, by means of prior certification by state administrations and an apostille, which, depending on the document, is affixed by the National Center for Information and Documentation, the Ministry of Justice or the Consular Relations Directorate of the Ministry of Foreign Affairs.
An apostille is a certificate with a stamp/seal certifying (legalizing) a document by the country that has issued the document. Documents bearing an apostille are exempted from any further form of legalization in countries which are members of the 1961 Hague Convention (see question: Which countries are members of the Hague Convention on the Abolition of the Requirement of Legalization for Foreign Public Acts?).
Legalization is carried out on documents that are to be served before a particular foreign state.