It's.....it's like the Everything brush set of everything EVER! Like I'd honestly never need to download another set, and I don't really need any of the ones I've already downloaded! YOU ARE AN ARTISTIC SAINT!
Oh dear...they are used for an application tool of the Adobe Photoshop series. It's a software for image manipulation, digital painting, as well as many other possible applications in arts. That's what most good artist here use for making their stuff. However, this seem like a downloadable package for using these ones.