The Web Dashboard is a client-side control which communicates with server part using HTTP requests:
The client part is the DashboardControl that supplies end-users with a UI for designing a dashboard and interacting with it.
The server part handles client data requests and provides various backend capabilities such as accessing data, storing dashboards, etc.
The client communicates with the server part using a RESTful API, allowing to you send multiple data requests simultaneously. For example, if you change the master filter in a dashboard containing several detail items, all these items send their queries to the server. These requests are independently processed on the server side for better performance.