# Glossary

## Glossary

| Term | Explanation |
|  --- | --- |
| Application | Your Sinch *Application*. Manage apps in the [Developer Dashboard](https://dashboard.sinch.com/voice/apps) |
| Application Instance | One installation of the application on a single device. |
| Application Key | The key uniquely identifies your *Sinch Application*. A key looks like `d404a4d3-51cf-45e2-bc32-e294ae879d58` (lowercase hexadecimal formatted UUID). |
| Application Secret | A secret used to for authentication and authorization. A secret looks like `oYdgGRXoxEuJhGDY2KQ/HQ==` (Base64-encoded string representation). |
| Callee | The user receiving a call. |
| Caller | The user making a call. |
| User | An end user. |
| User ID | Identity of a User in the application domain. |
| Active Connection | A socket connection for signaling purposes where incoming calls are received. |
| FCM | Firebase Cloud Messaging - Google Push Notification Platform |
| HCM | Huawei Cloud Messaging - Huawei Push Notification Platform |
| HMS | Huawei Mobile Services |
| HMS Push | The same as HCM |