On-premise PBX
incorporates the traditional telephone system installed on site (hardware or software) that is operated by the owner.
Hosted PBX (private)
The IP-based telephone systems segment begins with hosted PBX, which is still owned by the user (private), but is no longer located on their own premises and can be serviced by a third party.
Cloud PBX (public)
Multi Instance/ Multi Tenant, Single Instance/ Multi Tenant