Inverting channels in Photoshop is a useful technique for creating various effects, such as duotones, high-contrast images, and color inversions. To invert a channel, simply select the channel from the Channels panel and press Ctrl+I (Windows) or Cmd+I (Mac). This will invert the values of the selected channel, effectively creating a negative of that channel.
Inverting channels can be a powerful tool for creating unique and interesting effects. For example, inverting the red channel can create a cyan duotone effect, while inverting the green channel can create a magenta duotone effect. Inverting the blue channel can create a yellow duotone effect. Additionally, inverting channels can be used to create high-contrast images or to invert the colors of an image.