This means that you will be able to use your WhatsApp account on Android, iOS devices, and PC as a standalone app at the same time without having to log out from any account.
According to the rumor:
==> Your main WhatsApp account on iPad (when the app is launched) without uninstalling it from your iPhone.
==> The same WhatsApp account on Android and iOS devices
==> WhatsApp on your computer (without the necessity for an Internet connection on your phone) using the UWP app.
For now, WhatsApp Web can only be used to access your main WhatsApp account on your desktop, but it requires your smartphone to have an active Internet connection before you can be able to get incoming messages.
It’s still under development and they have not given any time that the will launch the new update. As for telegram is the only Whatsapp kind of instant messaging app that has that very feature.