The Graph is an indexing protocol for querying networks like Ethereum and IPFS. Anyone can build and publish open APIs, called subgraphs, making data easily accessible. Subgraphs can be composed into a global graph of all the world's public information. This data can be transformed, organized, and shared across applications for anyone to query with just a few keystrokes.
Before The Graph, teams had to develop and operate proprietary indexing servers. This required significant engineering and hardware resources and broke the important security properties required for decentralization.