What's the ML file in the bedroom map for?

[Banana]

Ok, I'm trying to make my first blockland map with interior, and I was using the bedroom map as a reference.
Then I notice a strange ML file in the bedroom folder, which I have no idea what it is.
Is it something you must have or can you skip it?

[Ad Bot]

[Marcem]

LIghting, generated when you run the map the first time.