Roundtrip is the process of doing a postback on a web page and then having the server process the postback, generate a new page, and send the results back to the browser.
For example, if you created a simple web page that only had a button on it, clicking on the button would create a roundtrip (the browser sends the form back to the server, including the fact that you clicked the button, the server processes any code you attached to the button click event, creates a new page with the latest state of the page, and sends it back to the browser). That's one round trip.
Chat with our AI personalities
When using ASP .NET with C# .NET, we have server side scripting in C# language.
When an server side event is fired say when button with attribute runat="server" is pressed, the click event is fired which is written in C#.
Inshort when server side event is fired, request is sent to the server and server responses to this request accordingly. This trip of request and response is called as roundtrip.