GraphQL is a query language for your API, it allows clients to define the structure of the data they need, and the server will return only the requested data. It is an alternative to RESTful web services, and it is gaining popularity because of its flexibility and efficiency.
In ASP.NET, GraphQL can be used to create web services that expose data in a more flexible and efficient way. GraphQL.NET is a popular open-source library that can be used to create GraphQL services in ASP.NET. This library provides a set of classes and methods that make it easy to create a GraphQL schema, handle requests, and generate responses.
Learn more from the following resources:
- [Introduction to Graphql Dotnet in ASP.NET](https://graphql-dotnet.github.io/docs/getting-started/introduction/)