What's means with *.cube.* ? e.g. eng.cube.fold

[uponup]

What's means with .cube. , e.g. eng.cube.fold.

And how can I create those files?

Now, I can run the demo but only support english, I would like to add other language ,for example French. But I can't complete it, because I only have fre.traneddata but not have other lifes named ".cube"