The themes and purposes vary with every image. Sometimes I get commissions for covers and/or illustrations that tell stories or ask questions.
The possibilities are endless with digital art, although you may say the same about traditional art. Digital art gives you the possibility to undo and redo every step without having to start all over, you can work with layers and manipulate every part the way you want it to be. You can play with reality or create your own.
Although sometimes I miss the direct contact with my work, having to start all over is not always the worst thing to happen to you. The limitation of traditional techniques makes you think differently and allows the aspect of play into your work. That's why I always start to sketch my ideas with pen and paper before working digitally.
I use different apps and programs to digitally paint or manipulate images like Adobe Photoshop, Procreate or Krita.