Torrents have become extremely popular these days as a means to transfer files that in many cases include copyrighted material such as movies or music. However, this is not the reason for torrents existence and many people compare torrents to the likes of P2P programs such as Napster or Kazaa since they don't understand that BitTorrent
technology is essentially a method of transferring files.
P2P Programs vs. BitTorrent
Many people think that BitTorrent is just another file sharing program like Napster or Kazaa. This is not the case since Torrent is not a program but is instead a method of transferring files and there are many different programs available that can handle torrent files but none of them are the "Torrent Program".
Note: This isn't entirely true since the creator of BitTorrent (Bram Cohen) does have a Torrent program called BitTorrent which would be considered the original torrent program.
HTTP and FTP
An easy way to understand this is to think about your web browser. When you browse the web, the pages you look at have to be downloaded to your computer and this transferring of web pages to your computer relies on the Hyper Text Transfer Protocol (HTTP). You'll notice in the address bar of your browser that the every web page you visit starts with http://. This tells the browser to use HTTP to retrieve the pages, and HTTP is just a standard way of transferring those web pages to your computer.
File Transfer Protocol (FTP) is another example. It is a standard way to transfer files between computers.
These standard protocols allow computers to communicate to each other and request information. By following the standards you ensure that the computers will understand each other.
Now, consider that HTTP is a way of transferring web pages and that many people use Internet Explorer to do this, but you can also use different browsers to do the same job. Some people may use Netscape, others will use Firefox but because all of these browsers are HTTP compliant they will be able to connect and retrieve web pages from any website you visit. The same holds true for torrents. There are many different programs available that are "Torrent Compliant", which means they will be able to connect and transfer files using the Torrent method. Some people prefer certain programs over others but as long as the program follows the Torrent standard it will work just fine.