In GIMP terminology, a filter is a plug-in that modifies the appearance of an image, in most cases just the active layer of the image. Not all of the entries in this menu meet that definition, however; the word “filter” is often mis-used to mean any plug-in, regardless of what it does. Indeed, some of the entries in this menu do not modify images at all.

With the exception of the top three items of the Filters menu, all of the entries are provided by plug-ins. Each plug-in decides for itself where it would like its menu entry to be placed. Therefore, the appearance of this menu can be completely different for each user. In practice, though, the appearance does not vary very much, because most plug-ins come with GIMP when it is installed, and of course they are always in the same places in the menu.

Plug-ins are not restricted to just the Filters menu: a plug-in can place entries in any menu. Indeed, a number of GIMP's basic functions (for example, Semi-flatten in the Layer menu) are implemented by plug-ins. But the Filters menu is the default place for a plug-in to place its menu entries.

For general information on plug-ins and how to use them, see the section on Plug-ins. You can find information on the filters that are provided with GIMP in the Filters chapter. For filters you install yourself, please refer to the information which came with them.