Telemetry provides data about what's going on within a model-driven app or on the server. Telemetry is crucial as it allows you to get a profile of app usage, detect performance problems and app crashes. Without this data, the app or service is a "black box"; the only way to get insight if you have an issue is to contact technical support. Telemetry enables you to detect and measure specific operations to better understand whether things are working normally or something is negatively affecting the system.
You can also use telemetry to observe overall performance trends so you can proactively manage them rather than react to user incidents. With Application Insights, you can define conditions where you'll be alerted when a metric exceeds a specific threshold.
The below screenshot shows a sample count of users accessing from browser, mobile, or embedded applications:
You can find more information and technical details in this article: https://learn.microsoft.com/en-us/power-platform/admin/analyze-telemetry.