Make free calls to any other computer using the program. Like instant messengers, it uses nicknames rather than phone numbers.
You will need a microphone to talk with others. It is also recommended that you have headphones to avoid feedback from your speakers.
You can also connect to the traditional phone system through optional pay features. For example, the SkypeOut feature lets you make calls to ordinary phone numbers. You can also get a phone number for Skype, so that regular phones can reach you.