Pixel editing alters an image's pixel information. One changes, augments, 'repairs' imperfections by adding or subtracting pixels that are part of an image's original data.

While methods have evolved over recent years for minimizing the effect of this inherently 'destructive' (transformative) process – by using layers, masks and saving versions of an original as one makes intended changes, once changes to an original have been committed (the 'Background' layer in a Photoshop file) there is no going back to what you started with.

Many key repairs and image enhancements can be done instead within the totally non-destructive environment both Lightroom and Camera Raw provide. This is a better alternative for conducting most of the changes photographers wish to initially make to their digital images.

One need not be intimidated by an application like Photoshop; but one also needs to commit themselves to learning how this complex application actually works before jumping-in and using it on unreplaceable originals. If you live in Phoenix, Arizona you would do well to start with this program of classes. Really.