The list of feature they provide is incredibly big:
video chat / voice chat
telephone integration
they make it available to forward incoming calls
your texts/SMS can be viewed from your desktop
keep track with your social networks through your desktop/cell phone
provide full e - mail service
multi protocol instant messaging (Skype, MSN Yahoo, Facebook, G talk, Fringde) - screen sharing / file sending available
fax service (allows you to both send and receive faxes)
advanced features - voicemail to email, call records, emergency calling)
From what I have read this seems to me as the ultimate communication platform - everything is rolled in one app.