These menus are available by clicking the right mouse button within an image window. In general, the commands accessible via these menus all operate on the image (or on a layer of the image, or on a selection area) from which they were called. Typically these menus are referred to by the notation <Image> → menu → submenu.
Start a new image. Dialog allows you to specify a new width and height and the initial background color. This is functionally equivalent to the New option under the Toolbox → File menu.
Open an existing image. This is functionally equivalent to the Open option under the Toolbox → File menu.
Save the current image.
Save the current image and specify a filename and format. Some image
formats require a certain type of image. (To save as a GIF, for
example, the image must be in Indexed mode.) Only the formats
applicable to the current image will be shown in the file type
selector of the Save As dialog. If the By
extension option is selected (it is the default
option), the Gimp will attempt to guess the file format based on the
filename extension provided (e.g., given the name
quahog.png, it will try to save as a PNG file).
Equivalent to the Preferences option under the Toolbox → File menu.
Close the image.
Quit the Gimp.
A somewhat gratuitous (but actually kind of nice) feature; the Mail image option will mail the current image (either Uuencoded or as a multi-part MIME message) to a specific ...