GraphQL is a query language for APIs and a runtime for fulfilling those queries with your existing data. GraphQL provides a complete and understandable description of the data in your API, gives clients the power to ask for exactly what they need and nothing more, makes it easier to evolve APIs over time, and enables powerful developer tools. GraphQL's declarative approach to data fetching provides significant performance and quality-of-life improvements over a REST API.
GraphQL allows you to have fine-grained insights about the data that's requested on the backend. As each client specifies exactly what information it's interested in, it is possible to gain a deep understanding of how the available data is being used.
The use of GraphQL for eCommerce has been beneficial specially for businesses which have adopted a Headless Commerce architecture. Due to the decoupling of the frontend presentation layer from the backend commerce engine, the frontend is heavily dependent of the correct data transfer to the frontend. GraphQL fosters seamless data retrieval on the front-end allow businesses to build more unique experiences.