We first heard about WhatsApp’s anticipated feature of ‘Group invites via links’ last month, where a report by Android Police spotted few translation strings hinting about the possible plan by the company.

Now Android police has discovered that the Group links functionality is partially live in WhatsApp’s latest beta version 2.16.102. So if you have an invite link already then you can join the group but you can’t issue the invites to groups as of now.
WhatsApp group invite feature is essentially a way to get more people in a group without having their phone numbers. It will allow a person to create a link to join a group and then share it to other via different apps, so in that case anybody who has the link from anywhere will be able to join that group. Even further you may be able to generate a QR code, or write it to an NFC tag, and then share it with anybody or can put it on web for people to join. We’ll know more about this once the feature goes live for everyone.

Source: http://www.muyitechblog.com/2016/06/04/whatsapps-wpcoming-group-invite-link-feature-partially-working-beta/