Skype is a software application that allows users to make voice and video calls over the internet. It was founded in 2003 and has over 443 million registered users who can call each other for free. Users can also call phones worldwide for a nominal fee. The document provides instructions on downloading and installing Skype, setting up an account, adding contacts, making calls, sending files and using additional features such as screen sharing. It also discusses how Skype generates revenue through subscriptions for calling phones and uses in education.