Sometimes you go to a website and the page does not want to open for whatever reason. You might just click Stop and move on to another page. The stop button does not really stop the request, the server still tries to complete the request and send a response to the client even client does not exist anymore. Rather than clicking on Stop maybe you click Refresh which triggers another request when the first one is not completed yet.
This scenario applies to all database calls. It might take longer to run a query for a reason and simply you need to wait until you get a response from the database server. If it takes too much time, you might want to cancel the request and try to look at your query to make it faster. You can do that programmatically by using CancellationTokens.
Read on for more information about cancellation tokens and how you can use them.