Sitemaps are designed around the User Journey
In other words, the journey your user will take through every page on your website. See how our friend John Doe travels through the imaginary website example:
Homepage
John Doe visits the homepage and wants to learn more about the services that he sees in the 'Services' section. He clicks on the 'Learn More' button.
Services Page
John reads through the services and decides he wants to contact the team to set up an appointment to begin a new service. He clicks on the 'Let's Talk' button.
Contact Page
John completes the contact form on the Contact page and clicks on the 'Send' button.