As the web becomes more international, you may find yourself optimising for international sites. Whilst the differences in spelling may be an obvious place to start, there are also a whole host of different things to consider - differences in search patterns, cultural differences, user behaviour, which social media sites are popular, colloquialisms and more.
The basis of any good SEO company would be to increase the rankings of your client’s website, but if you thought you could just go to the local version of Google and check the ranking of your international site accurately from the UK or wherever you are based, you would be wrong.