GraphQL is a new and fancy way of querying data. Think SQL but new and fancy, and you can do it over HTTP. Like you can ask hey example.com/api/data, what are the users aged 42 and older, and it will shove a bunch of JSON in your face. Rude.
But also convenient, because of web and stuff. And it will give you the data in the exact or close to the exact shape you asked for. Meaning, you can say give me a first name, horoscope sign, and the third digit of the cousin phone number and GraphQL will say ‘lol wut? … here you go’.