Custom Languages

Hello! So, as of recent, a lot of "new" programming languages have come out written in Lua (Novascript, LuaLua, etc.)

I was wondering one thing. In Novascript, you can do

private s = new String("Hello world!")

How exactly is this accomplished? I thought you could only add functions, but apparently not!

I have looked through the code, and call me a fool, but I cannot understand it that well.
Any help?

This is how interpreteres work. They take the code and read it word by word, symbol by symbol executing what needs to be executed.

basically when it gets to Lua side, that entire line is interpreted to be

local a = "Hello world!"