The text discusses the Apollo Link library, which is designed to be a powerful way to compose actions around data handling with GraphQL. A link represents a subset of functionality that can be composed with other links to create complex control flows of data. Links are isolated parts of the control flow and can perform side effects, modify operations, or provide developer tools. The core concept of a link is its `request` method, which takes a GraphQL request and returns an observable. Links can be composed using the `from` or `concat` methods to create chains of links. The `split` method allows for directional composition, where different links are used depending on the operation itself. Links can be stateless or stateful, with stateless links being simple functions wrapped in the `ApolloLink` interface and stateful links keeping track of operations using a unique key. The library aims to provide flexibility and customization options for GraphQL applications, with the goal of becoming like react components on npm.