You can use up to four linked devices and one phone at a time. The messages you send and receive are synced, and you can see your messages on all devices seamlessly.
Yes, WhatsApp web and desktop applications are extensions of the WhatsApp account on your phone. Can I use WhatsApp on my computer and phone at the same time? The messages you send and receive are synced between your phone and computer, and you can see your messages across all devices. WhatsApp for Windows and Mac are extensions of the WhatsApp account on your phone.
