Every image contains at list one layer but you can have as many as you want. Layers are separate images which can contain transparent areas or different levels of transparency. People use layers to create compositions in Photoshop because every layer can be edited separately without affecting other layers or composition. Another advantage is because you can save layered image (PSD, PSB, TIFF ) and edit layers at any time you want. Photoshop offers several type of layers like Type layer so you can change typed text only for example. When it comes to save image you can flatten image or to save flattened version of image on disc and leave composition as it is with all layers for further editing at later time. In other words saved layered image serves as template which can be edited even after 10 or 20 years.
There are many resources and websites that offer information about Photoshop layers. Some of these websites that offer information are Adobe, Photoshop Essentials and Photoshop Cafe.
Photoshop layers may not import into After Effects if the file format is not compatible or if the layers are not properly organized in Photoshop. Make sure to save the Photoshop file in a format that After Effects supports, such as PSD or TIFF, and ensure that the layers are named and organized correctly for easy import.
Open the Layers window.
color layers is simply color layers
Yes, .psd files maintain the layers you create in Photoshop so that the next time you open your .psd file in Photoshop you can continue to work directly onto the layers.
To store image parts.
One layer.
To select all layers in photoshop for a PC open up your layers window (It is under window - layers), hold down the shift key and click on each layer that you want to group together or edit.
Flattening layers just merges all layers down into one. It reduces file size, but once the image is saved and Photoshop is closed, you will no longer be able to undo the change and edit those layers separately.
To manually align layers in Photoshop, select the layers you want to align, then go to the "Edit" menu, choose "Align" and select the alignment option you prefer, such as aligning them horizontally or vertically. You can also use the Move tool to drag and position the layers as needed.
I opened a new project in Photoshop Elements 6 and began adding layers. I'm at over 360 and it hasn't stopped yet :D My guess is, it will add as many layers as your computer can handle without crashing.
Don't know how it actually does it, but you can only save layered images in format that supports them. ie: photoshop native files .PSD or layered TIFFs. Jpegs can not be saved with layers.