What is locales?
Should I set my country speciffic locale?
Should I have multiple locales installed?
(just curious though, not having any problems..)
Locales are configurations, and settings, for your locale (location). Take for instance, date formatting. In the US it is common to use "MM DD YYYY", but most other places use "DD MM YYYY" - a properly localized application will format a date as appropriate for your locale.
Translations are also handled with this if the app has a proper translation.
So, the real question is: where are you from and what languages do you use when using your computer?