This page was printed on Feb 23, 2019. For the current version, visit https://help.shopify.com/en/api/custom-storefronts/storefront-api/reference/interface.
GraphQL Interfaces are a sort of abstract "parent object" from which other objects can "inherit" from. An interface has its own list of named fields that must be shared by implementing objects.
For more information, see the GraphQL spec.