For the last two years, developers at whatsapp have been working on the implementation of calls on WhatsApp Web/Desktop (note: you will always need a phone connection).
WhatsApp Calls started a beta test for calls and video for some fortunate users a couple of days ago. These users are seeing the calls button in the chat header on WhatsApp Desktop. It will allow users to answer voice and video calls on the WhatsApp desktop/web client in a separate window.
This feature has been rolled out randomly to some specific beta users, and is only available for only very few users at this stage, but it will be available for everyone within the next few weeks.
Earlier this year WhatsApp added group video calling to its mobile platform as demand for such services jumped during the pandemic. WhatsApp on mobile supports video calls for up to eight users, it's unclear, however, whether this group function will be extended to the desktop/web client, or whether it will support only individual calls initially.