What is the difference between AntiVirus and Internet Security software  

Antivirus does not have internet security but internet security may have antivirus. Antivirus protects and checks the files on your hard disk for virus and warns you as such. But Internet Security checks whether you are visiting any site containing virus or downloading any infected files. They have firewalls and many more security measures that a simple antivirus do not have. I think I have answered your question. Do you want to know anything more?

I agree, Basically Internet security Stops things getting in and warns you about dodgy sites etc whereas antivirus fixes things that might have sneaked through like trojans, worms and all the other nasty little critters! It is best to buy the whole package and make sure that it has security and antivirus.
You can actually go to the sites and often they do trial periods of like three months, ive never actually bought one as ive just gone through and downloaded all the trials from many of the sites as they cost quite a bit!

I don't bother with all of that! It really can get confusing at times! I just use one product on my system and that is Norton 360 and it does absolutely everything! It keeps you safe whilst surfing online and if you are one of those people that like to do online banking then you are also safe doing this. I haven't had any problems with Norton 360 and I would highly recommend this. Andrew

Anti-virus software is just a part of Internet Security software, which provides us more security measures and features while Anti-virus software just have few features.

Anti-virus software just fights viruses, worms and trojans they have signatures for. Internet Security Software, also include firewalls, anti-spam tools, e-mail protection, and sometimes, other tools for privacy protection. I recommend buying the individual products and making your own suite software. You see, typcially, a software manufacturer might make the best firewall, but that doesn't mean they make the best anti-spyware, or the best anti-spam.

For most security software companies, they usually make one great product, then trying to survive and compete, try to offer everything, like everyone else in their competitive class does, and you end up with a buch of machine-slowing software.