What is Lua?
Simply said, Lua is “something” (a so called script interpreter) which is made to allow a program to run another program internally. The trick in that is, that the internal program does not need to be there when the “outer” program is made, it can be loaded later, just when you need it.
This allows to make a program now but change its behavior later as needed. This is widely used in the OOBD script engine: The script engine is there from the beginning, but what it does is defined by the script which is loaded at runtime. Another script, another functionality..
Luckely Lua became quite popular in the last years, so it's available for all major platforms, like Desktop PCs, Smartphone and Mobile Phones.
There are tons of documentation about Lua available in the internet, so we'll not explain the wheel here once more, we'll just focus on how Lua works inside OOBD.