We’ve all heard the universal phrase “can you photoshop this?” Yes, Adobe’s raster/image manipulation software has become part of the English lexicon (at least American English). But is it the only tool out there? Short answer: no. Long answer: there are a number of programs that are free.
The one I have installed and use occasionally as the need presents is GIMP. The Gnu Image Manipulation Program (GIMP) has been around for quite some time and was actually the first FOSS program I recall using.
If you need to work with images (photos and such), GIMP is a good tool. You can adjust, paint, skew, filter, etc. most JPGs, PNGs and even RAW files. Prefer to ‘paint’ rather than ‘draw,’ then GIMP is probably better suited for you than Inkscape. Keep in mind that Inkscape and GIMP can compliment each other as well.
As with Inkscape to Illustrator, GIMP replicates many of the core functions of Photoshop. Does it do it all? No, but it’s not really meant to. Tools like Adobe have the benefit of millions of dollars in revenue to support development, which means more power and capability (in general). That’s not to say FOSS tools are inferior. It just means development takes a different path, but can create the same output in many ways, but might also present new ideas.
As with Inkscape, GIMP is cross-platform, which means it works on Windows, Mac, and Linux.
Are there others, besides GIMP? Yes, but I haven’t used many of them personally.