The concept of channels is very unique in Photoshop. It is not as easy to use as layers, and there are far more subtleties than layers and so on. It is a simplified operation tool based on the color mode.

For example, an RGB primary color map has three default channels: Red (red), Green (green), and Blue (blue). But if it is a CMYK image, there are four default channels: Cyan (cyan), Magenta (magenta), Yellow (yellow), Black (black). It can be seen that each channel is actually a separate channel of a certain basic color in an image. That is to say, the channel uses the color value of the image to modify the image, and we can think of the channel as a filter in the camera.