What is really happening

Hello:

By clicking on that taskbar icon that allows for NIC configuration, I know
that when I check the box that says "File and Printer Sharing For Microsoft
Networks" this allows other computers to access resources on your computer
using a Microsoft network.

* However, can someone explain to me exactly what is going on in the
background or behind the scenes when this box is checked/unchecked ?
* How are the computer resources made available/unavailable when I
check/uncheck this ?

Thanks.