Standard colour image. Same as RGB image.
In most cases you should not perform image processing with BGR/RGB images.
Hue, Saturation and value. Hue = dominant color; the names that we give to colors (such as green, yellow, blue, and red) correspond to the different hue values. Saturation = how vivid the color is; pastel colors have low saturation, colors of the rainbow = highly saturated. Brightness/Value = luminosity of a color.
Colour images are composed of 3 channels. Each of these channels correspond to the intensity value of one of the three primary colors.
A BGR image is said to have 3 channels: a blue channel, a green channel and a red channel. A gray-scale image has 1 channel.