It's likely one of 3 issues:
1. Your Image Mode is set to Grayscale rather than RGB or CMYK.
2. The Layer Channel is set to Green or Blue and not RGB, which can make it seem like it's BW (for Image Mode set to RGB). If it's set to Multichannel, you can get the same problem if only the Alpha 1 channel is set.
3. If the image is a result of a scan, the scanner's setting is likely set to Grayscale and not Color.
First check the image mode - click on Image, Mode, then view the setting. Change it to RGB or CMYK depending on the project you're working on.
Next, check the Channel Palette (Window, Channels) and check that all channels are selected.
If it's not those, then check your scanner and make sure it's set for color output.
Layers are pictures stacked one to another, Layers can contain transparent pixels so you can see through Layer above what is on Layer below.
First click on layer with pixels you want to warp (layer can not be background layer, must be regular layer), in Photoshop CS5 and newer go to Edit > Puppet Warp or Edit > Transform > Warp.
You can desaturate an image in Photoshop by selecting the layer you want, and going to Image > Adjustments > Desaturate, or by pressing Shift+Ctrl+U on Windows, or Shift+Cmd+U on OS X. This will remove the color from an image or layer, and leave it in black and white. To have greater control over B/W conversion go to Layer > New Adjustment Layer > Black & White.
Layer > Layer Style.
Layer > New > Background from layer to convert regular layer to Background.
YES,but first you must convert it to pixels.in photoshop it is resterize layer command(right click on layer)
From Layer > Layer Style > Drop Shadow.
Basically Layers are pictures stacked one above another, Layers supports transparency so you can see what is below. See related link below answer.
layers are independent pictures stacked one to another,you can make for every stroke independent layer,and if there is something you did wrong or disliked you can change or simply delete layer and everything on layer will gone,or you can change colors for that layer independent from other layers and strokes
One layer.
Background.
Create new layer (click create a new layer icon at bottom of LAYERS panel or go to Layer > New