That's simply using an object oriented interface to a module. But to answer your question, modules can be viewed as language extensions. They use existing language syntax combined with their own documented interface. For more complex modules, learning the module's interface can be a lot like learning a sub-language.

Many of us here speak English, but many of us would be lost if we were asked to discuss a medical proceedure in medical terms. The medical terms are a subset of English (often based on Latin roots, etc.), but they happen to be a subset for which people outside of the medical industry are not proficient.

A new module can be a little like a medical journal that uses an unfamiliar subset of our familiar English language. You'll have to familiarize yourself with its terms (its user interface) before you'll be able to make sense of it. Fortunately, we don't need a degree in medicine to understand most modules' documentation...with the exception of modules written by TheDamian. ;)