The ".SU" domain extension is a bit unique. It was originally assigned to the Soviet Union, which doesn't exist anymore. However, the domain is still used today by some entities and individuals in countries that were part of the former Soviet Union. It's like a piece of internet history that's still around.

So, if you see a website with ".SU" at the end, it might be from a country that was once part of the Soviet Union, like Russia, Ukraine, or Belarus.

The ".SU" domain is suitable for individuals, businesses, and organizations located in countries that were formerly part of the Soviet Union. It's often used by entities in Russia, Ukraine, Belarus, and other post-Soviet states. So, if you're based in one of these countries and want a domain that reflects your regional identity, ".SU" could be a good choice.