Using Android Studio, MySQL, and php files, Where and how to save types of JSON responses

I am learning from the following tutorial. http://www.androidhive.info/2012/01/android-login-and-registration-with-php-mysql-and-sqlite/
WAMP PHP Directory
I came across this directory overview image and I also noticed some JSON responses in Section 3.3 Types of JSON Responses. I know they're echoes in php codes, depending on user registers and login successfully or not.
But I don't know how and where do I save such JSON files. The tutorial is quite quite detailed except this part. And I haven't dealt with JSON APIs and other objects yet.