Simply put, I think what the chap is demonstrating is a means to hijack wifi hotspot internet connection and have his own "server" masquerading as the internet. He sets up identical sites say facebook, twitter, tcu application site (chuckles) and in doing so, the patrons to this site will not know when they access their favorite websites, their access credentials are being tapped into a file that this user can make use of mostly in a destructive way. Luckily he is not completing the tasks in the video but since these tools are freely available it means this can easily be done.
ps. Above is in video up to 22minutes.
Lost your PC and assumed that since you had password on it then the most the new owner can do is format and re-install? Then better employ heavily built and intimidating men as bouncers guarding that PC you have those "important documents" in kwani, that will also be circumvented with tools available online, be it at a price.