GraphQL, developed by Facebook in 2012 and released as open source in 2015, is an API query language designed to improve efficiency in data retrieval by allowing clients to specify exactly what data they need, thereby conserving bandwidth compared to REST APIs, which return all available data. Unlike REST, which requires separate endpoints and multiple requests for complex queries, GraphQL uses a single endpoint and can handle complex data structures with a single query, making it ideal for mobile applications with bandwidth constraints. Companies like GitHub, Shopify, and Yelp have adopted GraphQL for its flexibility and efficiency, with GitHub citing its ability to replace multiple REST requests with a single GraphQL call, Shopify noting reduced server requests, and Yelp appreciating easy access to relational data. Despite its advantages, transitioning to GraphQL requires careful consideration of caching, query optimization, and API design, as outlined in guides comparing GraphQL to REST.