GIMP stands for GNU Image Manipulation Program. It’s the free alternative to Adobe Photoshop. Yeah, it’s free and it can do almost anything that you can do with Photoshop.
If you are into image manipulation and you don’t have enough budget for buying Adobe Photoshop, why not try GIMP? You can get a free download of GIMP here.
I am actually using it on my PC. Anyway, all I do with my photos is resizing, rotating and putting watermark on it. GIMP can do all of that. I don’t need the expensive Photoshop to do it.