Postman is an HTTP client that simplifies the testing of web services and RESTful APIs. Postman allows you to easily construct HTTP requests, send them, and inspect them.

Download Postman from https://www.getpostman.com/, and then install and run it:

1. On the introduction screen, click on the Request option:

2. Enter GetProducts in the Request name field, and then type GiveNTake into the collection section and create a new collection. Press Save to create the new request:

3. Enter the full URL of the GetProducts API (for example, http://localhost:5267/api/products) in the URL field:

4. Make sure that the HTTP Verb is set to GET and click on the Send button.
5. After a few moments, you should see the response that was received from your service, and you can now inspect the status code, response body, and headers: 

You will find Postman to be an indispensable development tool while you develop your APIs, and we will use it many times as we go deeper into ASP.NET Core in this book.

At this point, you might be wondering, how come the GetProducts method was invoked when we navigated to /api/Products? To answer this question, we need to talk about how ASP.NET Core routes requests into controllers and actions.