Skype is a popular cross-platform application which enables users to make voice calls over the Internet.
It also supports additional actions, like file transfering or instant messaging, as well as video conferencing.
Considering Skype becomes more and more popular with every update, developers have started creating tools that would increase the VoIP client's features.
These utilities can be either standalone applications, or they can be integrated within Skype, and their functionality ranges from entertainment (adding games or modifying the caller's voice with effects) to answering machines or translating features.