Yahoo Messenger is Yahoo's instant-messaging client and chat protocol. Yahoo Messenger users can chat with one another via text, voice, or video chat. Yahoo has also built-in VoIP services to let users call regular old telephones without having to leave the application. Users can also download and install a number of plug-ins that add extra functionality and features.
The latest version of Yahoo's Messenger desktop software lets users share files up to 2GB in size and includes "stealth" settings that let you choose who's allowed to see you when you sign in online.