Here is the simplest useful Pixie Script. The output from it appears to the left. Let's take a look. The first line starts with PixieVersion and a number in brackets. Anything between that and the end of the line is ignored by the script.
Comments can appear almost anywhere.
They serve as documentation - little notes to remind yourself what the script is doing in case you forget when you come back to it in 6 months time. Next we have a Header and a Body. This Header is empty. Usually it contains commands that apply to the whole image, but they all have sensible defaults so this script leaves them alone. The Body section contains the bulk of the script.