Rather, it's not like GIMP, paint.net, etc. kind of art program, though I guess you could probably use one of those to do the same thing. I can't really explain it in a way that makes sense to even myself. It's kind of like GIMP is more aimed at image manipulation and so their brush engine isn't quite as nice feeling as stuff like SAI, MyPaint, Krita, OpenCanvas, etc which seem keep in mind about tablets. So rather than like pixel art, IMO it would probably be for stuff leaning towards paintings. It also has a number of features that are kind of spiffy, even though I don't know how to really use them.
I'm not exactly an amazing artist by any stretch of the imagination, but stuff like SAI, MyPaint, Krita, etc just feel better when I want to draw something on the computer almost like I would on paper whereas with GIMP, I would probably be trying to clean up, add finishing touches, or just random alterations to a picture. In terms of those kinds of image programs, SAI is liked by a lot of people...but hasn't had anything done to it in the last 6 years (latest release was 2008), FireAlpaca may or may not still be developed (it's recent-ish though no linux support :/), MyPaint is my favorite on linux (primarily have a GTK desktop) and although it's being developed, it's development speed is not exactly blazing fast (they don't have a donate button either), OpenCanvas isn't free and honestly I'd rather just go for SAI (also not free) if I had to choose between them. Krita is kind of the only project that is open-sourced, has some pretty strong development, is free and cross-platform (ish...though 75000 euros and apparently they will get a Mac and port it to that too).
Some time back I went and tried all the general drawing applications that were prominent recommends (at least the free/trial ones). I actually made a post about it on
my blog (which is my blog to primarily me, to remind myself what my opinions are on certain programs, etc.).