New to otel need to clear my understanding on instrumentation

[Amangiri99]

Let's say I have a nestjs application and I am using apollo server as my graphql server. I have also added graphql instrumentation for the traces. There are few different kind of traces provided i.e: graphql.resolve, graphql.parse, graphql.validate.
What will be flow of execution is the hooks provided by the instrumentation is called first than the resolver is called? How is the hooks called? do the apollo server have an internal implementation were they call the hooks provided by the instrumentation?

I have spent a few time on this, but still haven't got my head around the concept of instrumentation.