How to tell which stream to use

[moth2daflame]

I have a Bluray documentary savedto my HDD. Using BDinfo i can see it has two streams, roughly same size (just slightly different size), opened it with VLC and they are exactly the same.

Question is why are there two streams of the same thing? Is there way to make distinction without actually putting the discin Bluray player?

[moth2daflame]

Let me restate that question again. I meant How do I determine which playlist from BDinfo correspond with which play option found through the Bluray menu.