When you have more than one distinct question, please
post them separately.

1) URLConnection is used for certain, specific protocols,
like HTTP. There are a number of Networking FAQs
which will show you how to send and receive data via
HTTP using URLConnection. Please search the FAQ for
them.

2) The use of that constructor is well documented in
the API documentation. Reference is also given to
the URL RFC, which you can read if some of the terms
are unfamiliar to you.