## Call Model

| Concept | Description |
|  --- | --- |
| **Session** | A session initiates as soon as the first call is created. It serves as a container for all related calls and their connections, maintaining context and state throughout the interaction. The session persists until all associated calls are terminated. |
| **Call** | A single participant's connection in a session (e.g., caller or callee). | **Inbound Call:** A call initiated from an external source (PSTN, SIP, etc.) into the service. | **Outbound Call:** A call initiated by the service to an external destination. |
| **Bridge** | A mechanism to connect one or more calls, so that participants can communicate with each other.
![session bridge chart](/images/voicev2/voicev2-session-chart.png) |