"GIMP is an acronym for GNU Image Manipulation Program. It is a freely distributed program for such tasks as photo retouching, image composition and image authoring.
It has many capabilities. It can be used as a simple paint program, an expert quality photo retouching program, an online batch processing system, a mass production image renderer, an image format converter, etc.
GIMP is expandable and extensible. It is designed to be augmented with plug-ins and extensions to do just about anything. The advanced scripting interface allows everything from the simplest task to the most complex image manipulation procedures to be easily scripted."
While GIMP does not offer the latest features found in Adobe's Photoshop, it is a very powerful and capable image editing program. Unfortunately, GIMP's interface is not as user-friendly as Photshop's. For someone who is used to working in Photoshop, GIMP can be especially cumbersome.
Thankfully, there is a book that may be able to help:
The Book of GIMP: A Complete Guide to Nearly Everything
GIMP is a free alternative to Adobe Photoshop with tons of professional-grade features. But with so many powerful tools and menu options, GIMP can be difficult to master. Whether you're struggling to get started or trying to master some of GIMP's more complex features, you'll find the answers you're looking for in The Book of GIMP.
The tutorials in the first half of the book walk you through essential GIMP skills, like resizing and cropping images, touching up spots and scratches, and customizing your work area. Illustrated, step-by-step instructions show you how to:
The book's second half offers a comprehensive reference to GIMP's many features, including color balancing, masks, filters, and plug-ins. You'll find tools described in unparalleled detail, with coverage of nearly every option and parameter.With illustrated tutorials and detailed references, The Book of GIMP is sure to become your one-stop guide to just about everything GIMP.
Amazon has The Book of GIMP: A Complete Guide to Nearly Everything available for purchase.