A link lets somebody join the workspace as a member for 30 days. Admins always have the button. Workspace settings › Members has a switch, off until an admin turns it on, that lets everybody who may invite people copy a link too; it lists every live link with who made it and Revoke. Turning the switch off again stops the links members made.
Copy an invite link to your workspace
Invite people in Kemble Work has Copy invite link, for admins — and for whoever may invite, once an admin allows it.