Internet
An internet site is a normal site that anyone on the internet can access (e.g., www.msn.com, www.microsoft.com, etc.).
Without Username and password anyone can access the site.
Intranet
An intranet -internal network
Intranet sites are hosted on the Web, can only be accessed by people who are members of the network.
They need to have a login and password that was assigned to them when they were added to the site by the site administrator.
(its like an our office we will use the sharepoint site for our development.)
Hope you have enjoyed after reading this small information.