In the second phase of the #100DaysOfGatsby coding challenge, participants, taking on the role of the character "Dev," are tasked with launching the website for a fictional startup, AudioC0RE, using Gatsby. The goal is to achieve high Lighthouse scores in areas such as Performance, SEO, Accessibility, and Best Practices, with the hope of attracting attention from Google's Developer Relations team. To accomplish this, developers must utilize the Chakra UI component library for site design, create a contact page with Formium, and deploy the site using a CDN while continually assessing Lighthouse scores. Key technical requirements include optimizing images with Gatsby's new plugin, replacing React with Preact, and implementing Progressive Web App capabilities to ensure offline functionality. Participants have three weeks to complete these tasks, and are encouraged to engage with the Gatsby community for support and guidance throughout the process.