CODE: This is when a desktop or mobile agent generates a URL to send to a guest to connect. This url contains a call url and a pincode.
ACD: ACD means Automatic Call Distribution, these are calls initiated by a guest, that are then routed to an Agent. Usually they will click on a pre-existing URL to connect to certain "type" of agent (based on skill or location routing)
Direct: (Deprecated) Call an agent direcly
Mobile: Similarly to the CODE call method, except specifically designed for Mobile Agents