Gives access to more than 20 blockchains: blocks, transactions, transfers, smart contracts, tokens
API allows to build various analytical queries above. the on-chain data collected from full nodes of over 20 blockchains.
Blockchain data is organized in types of blockchain ( ethereum, bitcoin, binance, etc. ). Every type is a top level node in GraphQL. The type accepts the argument - the network you need to access. For example, ethereum node accepts the network as ethereum and ethclassic.
The best way to explore API is to look at https://explorer.bitquery.io/ - multi-blockchain explorer, completely built using this API. Each widget is accompanied by GraphiQL button to explore the actual query.