In simple terms Phreeze is a framework for building PHP applications. A framework is basically a toolkit of helper classes along with a consistent application structure.
Phreeze is comprised of three components. A typical Phreeze application will use all parts of the framework, however they can be used independently of each other. The three components are:
The suggested way to get started with Phreeze is to utilize Phreeze Builder to generate an application. The application that is generated is a basic database editor that allows you to view, search and modify data from your MySQL database. This application is usable and may be sufficient for certain internal administrative utilities. However for a public facing website you would use this application as a starting point for your final product.
The Phreeze MVC Framework implements the Model-view-controller design pattern which is commonly used in web appliations. You can read more information about MVC design pattern on Wikipedia. The MVC allows you to organize an application into three parts so that you can achive separation of concerns - meaning each part of your code serves a specific function and can operate independently of the other parts.
The "Model" represents your data. In the case of Phreeze, the Model is a one-to-one abstraction of your database tables into PHP classes. For basic interaction with the database you don't need to write any SQL code, instead you can query and write using objects and methods in your PHP Model classes. The Model layer is not concerned with any visual display of information on the site. It deals only with translating between your application code and the database. Model classes aren't required to be tied to a database, they can also be used to abstract any information. However in the basic app generated by Phreeze all Models are tied to a database table.
The "View" layer is comprised of the classes that output the visual display. In the case of a web application, view classes will generally output things like HTML or JSON. The view layer is not concerned with where data comes from, rather is expects data to be provided to it in the form of Models. To give you a practical example, you may have multiple views for the same page in a web application. One view may be optimized for browsers and the other may be optimized for mobile devices. Your application will have the same back-end code for both, but the multiple views handle the different displays.
The "Controller" is a class that ties together the Model and the View. The Controller receives input from the user, reads and writes data as necessary using the Model and then determines which View to output. Controllers do a lot of the descision making for the application.
There are other design patterns in use on websites, but the MVC is a popular one that is particularly suited to web applications. These three components work together to provide a flexible app that can grow in complexity while keeping the code organized.
The Phreeze ORM are the classes that are used by the Model layer and handle the communication between your classes and the database. ORM stands for "Object-Relational Mapping" which basically means mapping an Object to a relational database. More in-depth information about ORMs is available on Wikipedia
Ultimately what an ORM does is let you work with classes and objects in your application and some lower layer of the code figures out how to write the correct SQL statements. In an ideal world you can think of this layer as a black box that you don't need to understand. But eventually when you need to do a more complex query you have to dig into the ORM to make it do your bidding.
Mapping a database to classes is fairly easy if you have no relationships between the tables. Any non-trivial database, though, will have foreign keys and constraints. Mapping these conceptually to a database gets more complicated. If you are a developer who utilizes complicated queries in your applications, it can be very challenging to use an ORM because it puts a new layer between you and your schema which may not offer the most efficient access to the data. This is sometimes referred to as an object-relational impedence mismatch. Different ORMs have different strategies for dealing with this problem. Some provide an abstracted query language that you need to learn. Some simply handle relationships badly and result in poor performance. Phreeze take the approach of handling the basic code, but allowing you to override things with your own SQL code when necessary.
The final component is the Phreeze Builder. This is not technically part of the Framework itself because the builder is not utilized by Phreeze applications. The builder is a utility that analyzes a database and auto-generates a basic application that is ready to use and/or customize.
The builder is not require to use the Phreeze Framework. You can write your code entirely from scratch utilizing the Phreeze libraries. However, as with any PHP application there can be a lot of setup involved. This can include setting up include path, requiring libraries, instantiating framework classes, etc. The builder makes this easy for you by generating all of this somewhat tedious code as well as generic controllers, models and views for each table.