levels adjustment layers

So I am stuck on levels so here is another trick I just learned.

What are levels in photoshop? to quote someone else...

"Levels is a tool in Photoshop and other image editing programs which can move and stretch the brightness levels of an image histogram. It has the power to adjust brightness, contrast, and tonal range by specifying the location of complete black, complete white, and midtones in a histogram. Since every photo's histogram is unique, there is no single way to adjust the levels for all your photos. A proper understanding of how to adjust the levels of an image histogram will help you better represent tones in the final image.

That is great, but I don't undersant the histogram or how levels work, and I don't really want to. (What I know about levels is that you use the white dropper and click on an area that should be white, or the black dropper and click on an area that should be black, and see what you get)
BUT I learned that if you go to do this, then something magic happens.
You start with a pic like this that needs help in the lighting area



Then go to Layer>New Adjustment Layer>Levels

That makes the levels adjustment come up in a separate layer. That is great, because if you are like me, when you use levels the pic can look like this.

Too much of a good thing.

But, now because the adjustment is in a separate layer I can play with the opacity of it and get this, without having to mess with the levels box for an hour:)