Irrlicht Engine

What determines the number of mesh buffers a mesh contains? For example the following code obtains a count of meshBuffers from an instance of an IMesh:
Are mesh buffers related to the objects a mesh contains? For example if you have a mesh which is a map that was modeled in blender, and when that map was modeled it contained a mesh for "floor", "door", and "wall", would you then have three mesh buffers one for each object in the scene? Or are mesh buffers something totally different?

It's at least one meshbuffer per material. Usually it's exactly that. But can also depend somewhat on the format (the meshloader basically can decide when to create a meshbuffer - only requirement from Irrlicht is that each material needs to have a meshbuffer).

one mesbuffer=one material.

A mesh contains several meshbuffers. You can append as many meshbuffers as you want to a mesh, or the loaders may append as many meshbuffers as necesary, but for the mesh scene node, a IMesh and its meshbuffers are a single entity, a single object, just with several objects that can vary the rendering properties across them.