USMT - What is default data backup/restore

Hi

We're using USMT and enabled the SMP role  

So far the USMT is working fine but I'm curious what is default info backup by the USMT

First it copy the files in our server \\sccmsvr\usmtfile and then restore

My I know whic files or folder backup by the USMT by default without any customization

a.  Windows  ?? 

b.   Document Setting  ??

c.  Program Files  ??

d. Registry ??

Please advise

e. Applciation ??