Creation and Order

• You can create a new layer by pressing the second-to-last button listed at the bottom of the Layers box that looks like a square with a corner turned up. A new layer will automatically appear named according to the number of layers that exist. You can change the name by double-clicking the word "Layer #." You can also change the order of the layers, which can effect what is visible, by clicking and holding down the mouse while dragging a layer to whatever order you like.
  
  

Blending Modes

• You can make the layers interact with each other according to their colors or values by choosing a different blending mode. This mode defaults as "Normal," but you can click the drop-down menu at the top of the Layers box to access 25 other blending modes. For example, choosing "Overlay" allows you to blend a layer into the layers below it, resulting in a ghostly-looking image. "Difference" makes the layer appear as the color and value inverse of the layer below it.
  
  

Quick Options

• In addition to the new layer button at the bottom of the Layers box, there are six other buttons for layer options. The image of a link allows you to link two or more layers once you click them while pressing "Control." The button marked "fx" applies effects to the layer such as "Drop Shadow" as well as nine others. The circle within a square applies a layer mask which allows you to make transparency changes without damaging the layer itself. The black-and-white circle applies a new "Fill" or "Adjustment" layer, letting you create color casts or adjust contrast. The image of a folder creates a group to organize layers. The trashcan deletes whatever layer is highlighted, or you can select a layer and drag it to the trashcan.
  
  

Opacity vs. Fill

• The upper-right side of the Layers box contains two sliders for "Opacity" and "Fill" that default to 100 percent. Using the Opacity slider allows you to control the transparency of a layer along with its effects, while "Fill" only adjusts the transparency of the layer itself. For example, if you have a text layer to which you have applied a glow, adjusting the Opacity slider changes both the text and the glow, while changing the Fill slider changes the text but not the glow.
  
  

Saving and Flattening

• If you want to retain the layers within an image, save the file as a .psd so you can make adjustments later. You must flatten these layers if you wish to use the image on the Web, however. From the Layers menu, you can click "Flatten Image" and save the file in a Web-format such as a .jpg. Once the image is flattened and saved, you can no longer make layer adjustments.