What is CHANNELS?
Channels palette does not store images (like Layers palette), but it stores information. The first four channels are color information.
If you click on Red channel -the image will appear black-and-white. But don't worry. You did not change the image. What you see is the amount of red color in the picture.
Click on Green channel - you'll see the amount of Green color, Blue channel - Blue color.
See the different color channels? They all look different because the amount of each color varies.
Click on RGB channel - it will display all three channels - the full color image.