Peer 2 Peer downloading is any program such as LimeWire, Frostwire, Bearshare and whatever program you can download to setup on your computer to get music, movies and even programs for free.
P2P downloading is not safe. Although many people use it, most people don't understand how downloading a simple music file onto your computer can cause a lot of damage.

I have seen over my time many computers come in that were infected with some kind of malware/spyware or a virus, and I can promise you that they came from programs such as listed above. How do I know? cause each computer had a P2P program on it. And if you think your virus or spyware program that you have is protecting you from this, think again.

Most of the more serious infections that come from downloading music/movies or misc. files will shut down any protection you have to allow itself to spread throughout your computer. Even a simple program downloaded from a music file can shut your computer down.

Another thing you need to consider when you are using these types of sites is the law. I'll start with this- there is no law preventing you from downloading whatever is on the net for personal use. Although they have tried, it's there and the net is for our use. Now here is were you are breaking the law- when you download something from the net, and than upload or share this you are breaking the law. You do not have the rights or permission to share whatever it is you downloaded.
Many people will say they do no share what they download, are you sure? Every P2P program that you can download and setup on your computer will automatically set itself up to share whatever you download. Programs such as Limewire will let you think you can shut down the sharing portion, but in reality you can not. They will always upload what you download. In the end, whatever you download from these sites, you are taking a chance.

Torrents, torrents are much better to use if you plan on downloading, but you still run the chance of getting infected or sharing information you have no right to share.

Bottom line, simply don't do it. If you want to take a chance of ending up in prison and having to pay a hefty fine, have fun downloading. If you want to keep things clean, stop downloading.