Analytic combinatorics is a calculus (set of mathematical tools) for analyzing properties of large combinatorial structures.
Book website of book videocourse
Result: A direct derivation of a GF equation (implicit of explicit), i.e. an equation that the Generating function must satisfy.
Classic next steps:
Result: Asymptotic estimates that quantify the desired properties.
Video course
Analytic Combinatorics, Part II (Analytic Combinatorics)
In Coursera: Analytic Combinatorics
Applications: Analysis of algorithms, Random deterministic automata, ...