What is the term for making an application that works within a website without a browser?

So basically, I want to make a program that works without a browser. For example, creating an auto login for a website within a program but it does not user a webbrowser. After auto logging in, I want the program to display in a textbox some of the data on the page? To sum it up, I want to know what this part of programming is called so I can research and learn about it. Thank you.