Apollo Client 3` is a state management solution that provides a more efficient and scalable alternative to traditional approaches like Redux or React Context. It introduces a normalized cache, which reduces the complexity of data storage and retrieval. The `useQuery` hook abstracts away complex data fetching, state management, and marshaling logic, making it easier to work with remote data. Apollo Client 3 also includes advanced cache manipulation APIs for power users, such as `modify`, `evict`, and `gc`. Additionally, it introduces Cache Policies and Reactive Variables, which provide cleaner patterns for local state management and enable cache reactivity. By using Apollo Client 3, developers can reduce the amount of custom code they need to write and focus on building their application's specific features.