Apollo is a GraphQL client that focuses on data fetching efficiency, while Next.js is a minimalistic framework for server-rendered React applications. Universal rendering combines the benefits of both by processing initial requests on the server and subsequent requests on the client. Apollo can be used independently to fetch data, but using it with Next provides significant performance and productivity gains. Next's file system API makes it easy to set up universal rendering, and its features such as automatic code splitting and hot code reloading further enhance development velocity. When combined, Apollo and Next enable developers to build applications that optimize for user experience and performance without sacrificing any aspect of the development process.