Usage of XAMPP and SQLITE3 for database management in Django

I am in the learning phase of Django.
While learning about Database integration, I was told to start the apache and mysql modules from XAMPP control to enable database connectivity to the local server and your app.

But I am unable to understand the whole functionality of the same and how to link the Django app and XAMPP servers.

Moreover I have downloaded a Django project from github where I am able to store, modify and delete the data from the app itself without even starting any of the modules from XAMPP.

I am unable to understand how is it able to work independently.

The project that I have downloaded also contains a sqlite3 file, the usage and accessibility of which is not understood to me in the project.

Please can anyone help me with the solutions of these 2 queries.