I think most of u must be already knew what is Aircrack...

and also it's function i think...? is it?

so in a simple words, it's a tool that let you crack the password (mostly WEP) from WiFI network arround ur device, by using unique packets & then decrypt the key from it... i can explain for detail, google it for more detail info, hehe

most of the time we will use this tool on our computer, with the main requirement is to find and use the network adapter that support this tool... and that's quite hard sumtimes