Layers shows the different layers in the current image and can be used to manipulate the layers. Information is available in Section 17.6.6, “Layers”.
Channels shows the color channels of the current image and can manipulate them.
Paths are a vector-based method of selecting parts of an image. They can also be used for drawing. Paths shows the paths available for an image and provides access to path functions. Undo shows a limited history of modifications made to the current image. Its use is described in Section 17.6.5, “Undoing Mistakes”.