An explanatory video:
So, What is BitTorrent?
BitTorrent is the global standard for delivering high-quality files over the Internet. With an installed base of over 160 million clients worldwide, BitTorrent technology has turned conventional distribution economics on its head. The more popular a large video, audio or software file, the faster and cheaper it can be transferred with BitTorrent. The result is a better digital entertainment experience for everyone.
BitTorrent is a protocol (a set of rules and description of how to do things) allowing you to download files quickly by allowing people downloading the file to upload (distribute) parts of it at the same time. BitTorrent is often used for distribution of very large files, very popular files and files available for free, as it is a lot cheaper, faster and more efficient to distribute files using BitTorrent than a regular download.
you can find more Frequently Asked Questions here.
To be able to open a torrent file and use it you need to download a torrent client, you may download Bittorrent client from this link.
install a torrent client, to software post search for the word torrent and when you click on it, it should start downloading a file or send you to a page where you can download the torrent and you will see that it opened in your torrent software, you may see how much is download and how much is the download speed including all the information regarding the torrent in the torrent client.
If you have any question feel free to ask and I will try to answer them as quick as I can.
Hope you have fun.