Having been (and still am) a CorelDraw user, when I started using Photoshop one of the things I had the most trouble understanding was layers. Each program handles layers differently. So let's talk layers in Photoshop.
The bookmark shown was made as a promotional give-away at a writers' conference. There are four text layers and six graphic layers making it a good example for this article. To start I created a new document that is 2" x 8", Resolution 300, CYMK Mode and Transparent for Contents. The high resolution and CYMK mode are selected as the bookmark will be printed. Transparent content provides a transparent background instead of white.
Then I started pulling the pieces together. The text came from my business card, copied and pasted from PageMaker and some of it was typed in directly as a new layer. The background was a gradient fill done in Photoshop. The decorative borders and pen came from my clipart collection. The @ and insert character were drawn using a red marker and scanned directly into Photoshop. And the pen tip bullets are from a wingding font.
The Layers menu lists all the layers on the bookmark. If the Layers box is not open, click on the Windows menu and select Layers from the list. The "T" shows which layers are text and also include the first word(s) so you know which "T" goes with each layer of text. The remaining layers are numbered and there is a small picture associated with each.
The eyeball image next to each layer listed lets you know that the layer is visible. Clicking on the eye makes the eye invisible as well as layer. See in the illustration that the eyes for Layer 4 copy and Layer 4 copy 2 have been clicked and the decorative borders on the bookmark are no longer visible. Clicking back on the boxes for the two layers will make both layers visible again.
To make changes, in this case on the bookmark, click on the layer in the Layer menu that is associated with what you want to change. For example, at the bottom of the Layers menu is Layer 3 and the image associated with it is a gradient fill. This represents the background. When selected the background of the selection in the Layers menu turns blue indicating that is the item selected. While selected you can make changes to the background layer -- possibly changing the color or direction of the gradient fill.
The same thing if you wanted to change the text or images. Clicking on the layer in the Layer box selects the layer to change. Clicking on the text layer in the Layers menu for Graphic Design Services would then allow me to change the text or move the selection within the bookmark.
The order of the layers is important. The layer at the bottom of the list is at the back of the bookmark and the layer at the top is at the front. The layers can be moved up and down the list by selecting that layer and dragging it up (or down) on the list. As you can see in the illustration, Layer 3, the gradient background, has been moved up the list and is now covering other layers of the bookmark. The layers are still there but since they are now listed below the background (Layer 3) the background image is covering them. Of course, moving Layer 3 back to the bottom of the list returns everything as it was. Layers can also be deleted by dragging them to the waste basket icon at the bottom of the window (not visible in these images).
Always save your work as a Photoshop file first before saving as a jpeg or other file format. Saving as a Photoshop file preserves your layers so, if you need to make changes in the future you will be able to. Saving your file as another format will "flatten" your image, merging all your layers into one. Once you flatten and save in a format other than Photoshop, there is no going back. So always save as a Photoshop file first.
The last thing on the Layers box that I would like to add is adding styles to your layers. As you can see from the second image above where Layer 2 is highlighted in blue, underneath you see Effects, Drop Shadow and Bevel and Emboss. These enhancements as well as many others are available by clicking on the first symbol at the bottom of the Layers box which opens the Layer styles dialogue box. Here you can add shadows, glows, overlays, strokes, bevel and emboss. As always, play around and try different things and have fun being creative!