Adjustment Tools

(1) Adjustment Layers in Photoshop allows you to make adjustments in your photo in a separate layer, maintaining the original photo's integrity.  You can also use them in conjunction with other features such as Blend Modes and Opacity.

In order to add an Adjustment Layer, you can select the Layer menu and choose "New Adjustment Layer" and select them from the list, or from the bottom of the Layers panel, you could select the Adjustment Layer icon and then select from that list.  

Don't confuse them with the options under Image > Adjustments. All of these adjustments under the IMAGE menu are permanent adjustments, meaning that if I apply one of them to my image, and then save the image, it's going to be very difficulty, if not impossible, for me to undo those adjustments.



Under the IMAGE menu, there are auto adjustments and changeable adjustment. See below:

(2) one-step adjusting - called Auto

(3) Adjustable tools that you can change -most are found under Image Adjustments

Under the tool box, you will also find other ways to adjust your image with the following tools:

(4) Adjustment tools on the Toolbar 

Finally, adjustment tools can modify different features on an image such as:
1) Lighting
2) Color
3) Blur