questions about Unity3d build -- file system

What kind of files should be built when unity3d publish build to android/ios:

1.which form : .txt? .png? .cs? .js?
2.which folder acceptable ? plugins? resource?
3.Why scene file such as *.unity could be built in any folder?
4.Where is the official guide for this?

oh… my God…

What is it?
What happened?
Are you okay?
Was it a trap?