Because the developers have considered that the average user does not need more functions than the ones included in the menus, Photoshop Elements did not inherit all the essential features as its more popular sibling, Photoshop. While this is not really an issue when you get started, the lack of some advanced functions as you progress becomes more stringent.
Elements+ for PSE is a plugin designed to reveal those advanced functions that you may need to minutely tweak your graphic designs. It is important to note that that undocumented features, in this case, does not mean that they are entirely missing, but rather that they are hidden from the user.
Upon launch, you need to patience for a few seconds or minutes, depending on the resources of your system, while the tool reconstructs its cache file. Afterwards, you can access the undocumented features via a dedicated dialog box. As a side note, you should bear in mind that these additional features are not officially supported.
Among the features you can use with Photoshop Elements once you applied the patch, you can count color channels, paths, smart filters, vector masks, so on and so forth. Moreover, thanks to the Scripts function, you can now automate operations that are commonly tedious such as extracting the EXIF data, for instance.