GIMP is free, an open-source graphics editing software program.
Supplied with many professional features which allow the user to perform editing almost to the level possible when using Adobes Photoshop.
Many of the standard features are easy to use and available for free, such as cropping, noise reduction, white balance correction, gradients, customizable brushes, and many more.
As mentioned above, GIMP is free and can be used commercially.
GIMP is compatible with GNU/Linux, OS X, Windows and more operating systems. It is free software and it is possible to change its source code and distribute changes. A powerful graphics editor with no cost!
Although GIMP is free, the features have not been compromised. The range and quality features make GIMP a fantastic, free, alternative to commercial-grade programs such as Adobe Photoshop. Supplied with all the standard and more complex tools graphic designers, photographers and illustrators need and expect.
In comparison to commercial-grade programs, GIMP has an interface on a similar level which rivals the high-end graphics program layout. The GU interface is easy to use divided into three parts. The main editing area, toolbox, and layer, paths, undo, and channels. Image thumbnails are displayed for the images currently loaded into the editor.
This said GIMP is free so commercial editing programs do have a level of features beyond its capabilities, but GIMP does provide all the essential features, commands, and tools. Additionally, GIMP also provides channel manipulation editing tools.
Various third-party plug-ins are available for GIMP which extends the options further.
Ease of use
The balance between technical features and ease of use has been managed well with the design of the GUI.
Icons show the various tools with a pane for tool settings.
As GIMP is a popular free graphics editor there are many tutorials, videos, and discussions available, so the answer to your question is available.