Modules in this section implement low-level APIs. These modules fall roughly into three categories:
building blocks for higher level modules, such as events, worker, and api-utils. You're more likely to use these if you are building your own modules that implement new APIs, thus extending the SDK itself.
privileged modules that expose powerful low-level capabilities such as tab-browser, xhr, and xpcom. You can use these modules in your add-on if you need to, but should be aware that the cost of privileged access is the need to take more elaborate security precautions. In many cases these modules have simpler, more restricted analogs among the "High-Level APIs" (for example, tabs or request).
These modules are still in active development, and we expect to make incompatible changes to them in future releases.