In it you'll find all the standard tools of photo-editing applications: color control, saturation, levels, brightness, etc. You can also extract color channels and apply posterization effects really easily.
Naturally, Pixelitor uses layers as an editing method, and incorporates all the necessary tools for working with them. In fact, the similarities with parts of Adobe Photoshop are quite impressive.
Pixelitor is a great alternative to large image editors like Photoshop or GIMP. Its features, optimization, and small size make it a highly recommended option.