In Photoshop, foreground and background are the two main layers that make up your image. Foreground is what’s in front of the layer, and background is what’s behind the layer. You can change the foreground and background of any layer by selecting it and clicking on the Background or Foreground button at the bottom of the Layers palette. This will open up a dialog box where you can choose which layer should be in front or behind the other. ..
