Back | Track 4 is a penetration tool, so you can use it to hack(or try) to hack into say, your wifi or something. I tested it out on my wifi - and i actually got the password correct, and using back-track, i was able to access my wireless router and change the password to the wifi, and also to infect the machine connected to the router(which was my dads)[but don't worry - i only wrote a script to shut down and not actually "infect" my dad's computer
This is back-track: http://www.backtrack-linux.org/w
And also, using a app in Backtrack ( called S.E.T[ social engineering toolkit]) i sent my-self an email with a cloned website(which was actually this website) and what it was - was i sent myself a link to a website ( which said http://sevenforums.com
) and when i clicked it, it bypassed my AV(which was Microsoft Security Essentials) and then using a meterpreter(just this one process thingy, can run commands) i told my "infection" to hide under explorer.exe and i then shut-down my computer(using a meterpreter command).
And i was able to learn/do all that after probably only like 8 hours of messing around with all the tools in Back-Track. If you wanna "hack" (but legally) hack - i would check it out. Really fun and cool. (I recommed atleast basic experience with Ubuntu/Linux)