Reactor is an Object-Relational Modeling (ORM) framework which generates database abstractions on the fly, as needed. Reactor is sometimes called an “Inline Dynamic Database Abstraction" API.
In simpler terms, Reactor is used to generate ColdFusion objects which are used to access data in your database. Depending on Reactor’s configuration, these objects are recreated as your database or configuration changes.
Reactor accelerates development by automating much of the repetitive, tedious and error-prone work involved in creating an Object Oriented database abstraction layer.
Based on unscientific observations, it is roughly estimated that Reactor can help save up to 20% of your project’s development time. For more information on this see this blog entry.
Because no code generator is perfect, Reactor generates a set of customizable objects which you update with your own code to add, override or enhance Reactor’s default behaviors.