There are not many people who I trust on the subject of API design like I do Phil Sturgeon. He has been a prominent speaker both online and at numerous conferences, covering a variety of problems, solutions, and approaches in the API design domain.
In one of his recent blog posts, he shared a diagram (see above) which provides a clear illustration on which API paradigm – REST, GraphQL, or RPC – one should pick for a web application, based on a variety of criteria.
I think this is probably the simplest of all the explanations I’ve seen around.