Localization could be defined as local upgrade of the translation. Localized translation is completely adjusted to target language and its speakers. Localization requires great knowledge of target language, local culture and other characteristics, connected to target language.
Localization is much more than just adaptation of correct spelling, correct writing of dates and numbers, changing values into local currency… It also includes complete graphic design, choice of colours, design of the message etc.
Localization is most needed in translations of websites, software and catalogues of products.