If you’re not familiar with Scheme and Guile in particular, here is a simple tutorial for you.
If you already know the basics of the Scheme language, please feel free to skip this section.
I would recommend newbies to type/paste the code in Guile REPL following the guide in tutorial: Learn Scheme in 15 minutes
And here’s a nice section in the Guile manual for basics in Scheme: Hello Scheme
Please don’t spend too much time on these tutorials, the purpose is to let newbies get a little familiar with the grammar of Scheme.