types of software : free/open source/distributable : free to download, distribute
paid : need money to buy those and then u ll be given a serial key to run it
pirated: paid softwares when converted to unpaid by getting into that software and changing some files or using hacked serial key illegally
when u download a pirated software., the person who makes it pirated leaves a worm which is undetectable and sends your information remotely via internet . or multiplies to slow down system