What is GraphQL and why would you use it?
GraphQL is a query language invented by Facebook. It's a query language that is NOT used to query data from a database though. Instead, it's exposed via an API to frontend applications (SPAs, mobile apps).
It's more flexible than REST APIs because it allows frontend clients to request exactly the data format the client needs. REST APIs on the other hand typically send back a fixed data format that often contains redundant data which is not required by the client.
Watch the above video to learn more about the advantages of GraphQL APIs and how such an API is implemented in practice.