Why is it necessary to have Incoterms? And what is the purpose of making amendments and additions to Incoterms?

Why is it necessary to have Incoterms? And what is the purpose of making amendments and additions to Incoterms?

The purpose of Incoterms is to provide a set of international rules for the intpretation of the most commonly used trade terms in foreign traden .Thus,the uncertainties of different interpretations of such terms in different countries can be avoided or at least reduced to a considerable degree.Amendments and additions are made in order to bring the rules in line with current international trade pratices.