You can invite members of the public to be community members. To do so you must be a community administrator.
Navigate to the Admin Centre of a community and click on Manage Members.
Click on the Add Guest Members tab and provide the required information.
This will create a guest account for the user.
User interface to add a guest community member
If you take this approach and invite members of the public to join a community please note that some of the public community members have limited access to certain functions.
Public users can't make their own discussion posts.
Public users can't vote in polls.
Public can't upload files or comment on files.
If you don't want community administrators to be able to add guest accounts, there is a database setting option you can use to restrict this ability to medtech:admin users only (community_display_guest_enrollment).