Question:What are Web sites & URL(s)? 

Web sites: A web site is a simply a group of file and folders which are stored on a WWW server and which can be freely accessed by people(s) “surfing the Web”. For instance Microsoft has Web site is www. Microsoft.com etc.
URLs: The address of a Web site is given but something called its URL (Uniform resource locator)

Question:What is a Firewall? 

A firewall is a system that secures our network from access by unauthorized users and a firewall is consists of software & hardware protection against invasion via the Internet.

Question:What is the Spam or Unsolicited email? 

Spam is one kind of unwanted E-mail(s). We should be very careful about entering our E-mail address forms on web sites which is not familiar with us. We may later get unsolicited E-mail (called spam) from the web site.