FOSS gamedev and creative worlds

I'm just starting out with a basic "hello world" mod to learn the API.

I did the first tutorial, and it seems like there is a list of properties that can be set for each custom node. However, I could not find documentation on these properties or what the number values assigned to them indicate. For instance, setting flammable=3. What does the 3 indicate?

Is this on the wiki, or am I out of luck?

Groups are specified on the Wiki, unfortunately it does not say what a '3' would mean for flammable.

http://dev.minetest.net/Groups

The most extensive documentation about the api (which also coveres all properties of nodes) can still be found in doc/lula_api.txt.