What I never understand about these things is ... what actually does the drawing? The AI decides what the beetle looks like, at what level of abstraction? When/how does it go from beetle idea to pixels? Does this network "know" what the beetle's "leg" is, or does it just "know" "this pixel here should be this color"?
One (the discriminator) is trained with a bunch of images showing what beetles can look like. It detects a real or fake image of a beetle.
The other (the generator) is just generating images with a convolutional neural network. The generator optimizes itself based on how close it is to passing the discriminators test - that is its "loss function".
So over time, the generator gets better and better at making things that look like beetles. The process takes a very long time and is aided by many GPUs (as mentioned in the article)