Layers???

OK, please don't slaughter me as I'm still a newbie, especially with processing, but I don't have a clue about layers and how they work or how to work with them. I can't afford to buy anything else at this point so I've been using GIMP. Usually when I pull up an image in GIMP I do unsharp mask, maybe color saturation, play with levels and curves a bit.....I can do a select and then sharpen and/or adjust levels for the eye area for example but that;s about the extent of my processing skills. Most sites I've found that talk about layers are applying it to creating something (like a logo) but not much info on editing images.

I really think I need to improve and advance my skills and knowledge of processing, so can some kind soul offer some explanation or point me in the right direction?

Many thanks.

Layers have a couple very important uses!

First and foremost, they give you the ability to do "non-destructive editing" -- you can put changes of all kinds in an image and, as long as you keep the "work-in-progress" layered file, you can go back to any stage, including the original -- you lose non of your work.

Second is the fact that much of what you do with layers can be adjusted after the fact -- similar to the first point, but fine-tuned. This can especially apply to what is in Photoshop Adjustment Layers, but can have broader applications as well. I haven't used the Gimp, so don't know how it handles layers, but at least one example would be a layer where you applied some brightness or contrast to an image, followed by other work. Layers allow you to pick one layer to adjust or (if need be) delete and re-do.

One more note -- a features that are typically associated with layers are:

The ability to select and isolate a portion of an image to edit -- this can be done without layers but putting a selection on a seperate layer opens up whole new capabilities.

The ability to create and work with a Mask -- may be doable without multiple layers but probably not nearly as useful. You can create a layer, apply some kind of adjustment, add a mask that "blocks out" that adjustment, then brush the adjustment back into a desired area.

Layers are one of the most important features that sets apart a "good" image processor from a run-of-the-mill one. Users of the Gimp are very fortunate to have such a supportive bunch of programmers to make this feature available in a free alternative to Photoshop.