Variables in GraphQL are a way to pass dynamic values to a query or a mutation. They allow the client to make a query more dynamic and flexible by passing in different values for the same argument. They are defined in the query or mutation using the $ symbol followed by the variable name and a type, and their values must be passed in a separate JSON object. They also are type-safe, this means that variables must be passed values that are of the same type as defined in the query.
To learn more, visit the following links: