Nothing "teaches" an invention better than describing one or more examples. Both actual working examples (which are described in the past tense) and hypothetical or "prophetic" examples (which are described in the present tense) are allowed (and, in fact, encouraged), but neither are required.
While the law requires that the disclosure be sufficient to teach the invention to a "person skilled in the art," the reality is that some patent professionals and some patent examiners are not familiar with the details of many fields within which invention occurs. It is also the case that "new matter" (additional disclosure of the inventive concept) cannot be added to a patent application after it is filed. For these reasons, it is better to err on the side of too much disclosure (by providing at least one very detailed working example) rather than on the side of too little.