The Adjustment panel allows you to apply color and tonal corrections to your image non-destructively, i.e., without making permanent changes to the underlying pixels.
About the Adjustment panel
The Adjustment panel presents color and tonal adjustments under adjustment type (e.g., HSL) as a series of preset thumbnails.
Selecting an adjustment type expands the view to show adjustment thumbnails, with each thumbnail applying an adjustment intended for specific uses (e.g., Desaturate); clicking on a thumbnail applies that preset.
The adjustment is added as an adjustment layer to your layer stack.
As you apply a preset you can fine-tune the preset's settings, optionally creating the modified adjustment as a new preset.
The following general settings are available from all adjustment dialogs:
Add Preset—adds the current adjustment settings as a preset for use with later images and projects.
Merge—merges the current adjustment layer with the layer immediately below it in the layer order.
Delete—closes the dialog and deletes the adjustment layer, removing the adjustment from the image.
Reset—reverts all dialog settings to default.
Opacity—how see through the adjustment layer is.
Blend mode—changes how the applied pixels interact with existing pixels on the layer below. Choose mode type from a pop-up menu.