|Shiver me timbers, the article be a Stub, arr! Maybe ye can help expand this sorry sight|
Each of the Nations has its own language. The Pirates speak a language called Patois and each of the Nations speak their own tongue. In-game this means that players from different nations by default cannot speak with each other. If someone tries to talk to you in a language you cannot understand you won't see what he said. Instead you will see:
<playername> said something in <language>.
There is a skill called Diplomacy which allows you to understand foreign languages.