The patent application goes into detail describing an optical system for use in a head-mounted display. This head-mounted device could be used for either virtual or augmented reality purposes — both are mentioned, but the emphasis, interestingly, is being placed on virtual reality.
Additionally, Apple notes that long-term use of a head-mounted device can be uncomfortable. The patent also describes its methods for mitigating this issue — namely the use of more efficient lenses that aren’t bulky or heavy.
Basically, Apple has invented a system that can display images or other content on a head-mounted device that incorporates more efficient and comfortable-to-wear technology.
Of course, since it is just a patent application, there’s no guarantee if we’ll ever see the tech described hit the market. So take these rumors with a grain of salt.