BitTorrent is a BitTorrent client originally created by Ludvig Strigeus (ludde), and is currently maintained by a team of developers at BitTorrent, Inc. A client is a computer program that follows the rules of a protocol. For example, HTTP (HyperText Transfer Protocol) is the protocol used for transferring web pages and other content, and your HTTP client (or web browser) is the program you use to get those web pages. Some popular browsers include Microsoft Internet Explorer, Mozilla Firefox, Opera, and Apple Safari. To an extent, they all work in the same way because they follow the same set of rules. Just as there are multiple HTTP clients, there are multiple BitTorrent clients that observe and conform to guidelines set in the BitTorrent protocol definition, and BitTorrent is one such BitTorrent client.
So what sets BitTorrent apart from other BitTorrent clients?
Micro-Sized Yet Feature Filled
Most of the features present in other BitTorrent clients are present in BitTorrent, including bandwidth prioritization, scheduling, RSS auto-downloading and Mainline DHT (compatible with BitComet). Additionally, BitTorrent supports the Protocol Encryption joint specification and peer exchange.
BitTorrent was written with efficiency in mind. Unlike many other BitTorrent clients, it does not hog valuable system resources, allowing you to use the computer as if it weren't there at all. Additionally, the program itself is very portable, being contained within a single executable small in file size.
Skinnable and Localized
Various icon, toolbar graphic and status icon replacements are available, and creating your own is very simple. BitTorrent also has support for localization, and with a language file present, will automatically switch to your system language. If your language isn't available, you can easily add your own, or edit other existing translations to improve them!
Actively Developed and Improved
The developers put in a lot of time working on features and making things more user-friendly. Releases only come out when they're ready, with no schedule pressures, so the few bugs that appear are quickly addressed and fixed.