The document discusses how Ruby's dynamic and reflective nature allows for meta-programming techniques that Rails leverages heavily, such as enhancing classes and using code as data, to accomplish its "magic" of providing a domain-specific language for building database-backed web applications with an integrated and seamless front-to-back stack. Ruby's meta-programming capabilities like open classes and meta-classes are key to how Rails accomplishes convention over configuration and allows terse and expressive code to generate advanced web application behavior.