GraphQL fragments are a powerful tool for optimizing and simplifying GraphQL queries by breaking them into reusable, modular components, thereby enhancing readability and maintainability while reducing redundancy. These fragments allow for effective management of complex queries and can be shared across different queries, fields, or aliases, providing a more streamlined approach akin to reusable functions in programming. They help avoid over-fetching by clearly showing which data is being requested, and when combined with GraphQL directives, they can further enhance performance by dynamically including or excluding certain fragments at runtime. The use of fragments also supports better caching strategies with GraphQL clients like Relay and Apollo Client, reducing redundant network calls. Best practices for using fragments include keeping them focused on specific data units, avoiding overly broad or deeply nested fragments, and colocating them with relevant code components to maintain clarity and scalability in web development. Contentful's Composable Content Platform and GraphQL API exemplify how fragments can be utilized in content-heavy applications to ensure organized and efficient content delivery, leveraging a global CDN for quick access even during high traffic.