Gatsby, a popular web development framework, was highlighted in 2020 as a key technology to learn, and the #100DaysOfGatsby challenge was introduced to help developers explore its capabilities. Challenge 12 focuses on transforming a Gatsby website into a dynamic web app by incorporating gated content, allowing only authenticated users to access private sections. This can be achieved through plugins like gatsby-plugin-create-client-paths or by building custom components, with resources provided to guide users through these processes. Developers are encouraged to experiment with authentication services, such as Auth0, and utilize community support channels if assistance is needed. Additionally, Gatsby offers examples and tutorials on how to implement these features, emphasizing its versatility for both websites and dynamic applications.