Although the words are often used interchangeably, localisation covers a wider scope than translation.
Translation
- turns content from one language into another (e.g. Japanese into English).
Localisation
- identifies and resolves cultural issues present in the content (religion, politics, etc.)
- adapts content to reflect differences in numbering systems, address formatting conventions and the like
- concentrates on making the translated content read, sound and look like it was written originally in the target language.
Most translators and translation projects will also localise to some extent, but to ensure the best possible result you should aim to cover more than just substituting the words of one language for another right from the start.
And needless to say, although machines may try to translate given access to large volumes of existing human translations, localisation is another matter entirely.