I wan to make a language category using the block:
What does '[msg] mean in the option dropdown?
Just don't.Use the library blocks that have an encapsulation.
I am a new snapper, so what is an encapsulation?
Do not enable Extension block, until you know for sure you need it.
You cannot add a new language to Snap! this way. You must modify the source code on Git Hub. I would not recommend messing with the extension blocks unless you know what you're doing.