Channel effects are used to manipulate the color and transparency channels in a layer.
This enables you to apply a standard blur to individual channels instead of the entire layer.
Used to mix the color channels together. The red channel can have some of the blue channel introduced to it, for example.
Replaces channels with other channels. For example, you can have a layer's alpha (transparency) set to correspond to its red values, or its saturation.
In this example the alpha channel is mapped to the red channel, resulting in a semi-transparent layer. This reveal the layer beneath.