Postman helps make HTTP requests with an intuitive UI. If you are not really a command-line person, you can use Postman for exploring REST APIs. You can download Postman from https://www.getpostman.com/apps or you can download the chrome extension from here: https://chrome.google.com/webstore/detail/postman/fhbjgbiflinjbdggehcddcbncdddomop?hl=en. Once you have installed Postman, you can launch it and sign up/log in if needed. Using the New menu on the top bar, click on Request. You will be asked to fill, a new request form; you can do so as shown here:

Now, create a new HTTP GET request pointing to https://reqres.in/api/users as shown here, click on Send, and you should see a response like this:

In this book, I am going to use Postman for making requests, primarily for ease of presentation. You can use any REST client you like.