Sapphire is quite new technology, some of its concepts may be not obvious.
This is article that will introduce you into Sapphire.
Content Management System
Sapphire is CMS like wordpress or joomla with own admin panel that can be accessed at https://sapphire-app.url/admin.
You can manage whole website or application there. It also has Content Managing System that allows you creating own collections with schemas and entries with many types, just like in database.
It has application editor (code monaco editor).
Framework
Sapphire is also a framework for creating applications. Sapphire supports layouts system for rendering pages.
Every layout is written in custom templating language called Onyx. Its supports custom components and scoped styles.
Also sapphire supports building custom apis and controllers for managing data stored in Sapphire Content Manager.
Extendable
With Sapphire built-in plugins system you can customize your application to all your needs.