Cataluyna (or Catalonia, as it's sometimes spelled in English) is the region on the northern Mediterranean coast of Spain, between Valencia and the French border. Barcelona is the capital of Catalunya.

Probably the biggest difference between Catalunya and the rest of Spain is that the primary language is catalan, which resembles spanish in some ways but is actually a separate language. Nearly everyone in Catalunya speaks spanish as well, but there's strong support for the catalan language as a part of the regional identity. There are other cultural differences too, and many catalans identify themselves as catalans first and spaniards second.

There's some really good information on Catalunya to be had on Wikipedia too, if you're curious.