According to WhatsApp’s announcement, “Today we’re introducing a desktop app so you have a new way to stay in touch anytime and anywhere – whether on your phone or computer at home or work. Like WhatsApp Web, our desktop app is simply an extension of your phone: the app mirrors conversations and messages from your mobile device.”
The app will be compatible with both Windows (will need Windows 8 or newer) and OS X 10.9 or later. This means users out there with older software platforms like Windows 7 will not be able to take advantage of this app. For now it looks like the desktop app will mirror the interface of its web counterpart, but hopefully WhatsApp will consider implementing a different UI in the future.
For those interested in getting their hands on it, just head on over to WhatsApp’s website, download the app, scan the QR code on their phone, and they’ll be good to go.