This document provides an overview of the Typelevel stack, including Cats, Cats-Effect, Http4s, Circe, and Doobie. It describes these libraries as providing abstractions for pure functional programming (Cats), modeling programs as values (Cats-Effect), building HTTP applications (Http4s), working with JSON (Circe), and interacting with databases (Doobie). It includes examples of using the Http4s DSL to define an HTTP service and using Doobie to run database queries.