Well here are a few explanations as to what a Virus, Trojan, Nuke Attack and the many other things that can happen to you without these tools, especially if you download files off the net or visit chat rooms. Virus A program or piece of code that is loaded onto your computer without your knowledge and runs against your wishes.
Most viruses can also replicate themselves.
All computer viruses are manmade. A simple virus that can make a copy of itself over and over again is relatively easy to produce. Even such a simple virus is dangerous because it will quickly use all available memory and bring the system to a halt. AntiVirus A utility that searches a hard disk for viruses and removes any that are found. Most antivirus programs include an auto-update feature that enables the program to download profiles of new viruses so that it can check for the new viruses as soon as they are discovered.