Since you are a newbie you should go wikipedia.org and search for the basic things. For instance here is what they say about firewall http://en.wikipedia.org/wiki/Firewall_%28networking%29

__________________
Liens d'intérêt /Links of interest:
Gnutellaforums en français /The House's rules you have to respect / First search the forum, then create a thread / Free software alternatives! - Logiciels alternatifs gratuits!/