A software application that is "localized" is one whose user interface has been translated into one or more target languages. According to the Localization Industry Standards Institute, Localization is defined as: "...taking a product and making it linguistically and culturally appropriate to the target locale..."
It is difficult to think of a software application that can be localized without first being internationalized. If the software doesn't work on local-language operating systems, there really is not much point in spending time, money and effort into having its user interface localized into the target language.
Localization is the complimentary process to internationalization, and includes the activity known as translation, but is a far more extensive process, and includes:
• Project management.
• File format conversion.
• Image translation.
• Engineering and DTP
• Linguistic testing.
• Functional testing.
Localization is often known by its short form, L10N, where the "10" refers to the number of letters between the "L" and the "N".