What is Oracle Problem?

The oracle problem refers to innefficiencies regarding the introduction of external data to isolated blockchain systems. By default, on-chain network protocols are unable to obtain external data. Isolation makes blockchains very secure and reliable, but also makes it difficult to obtain and share outside data used by smart contracts. Data oracles exist to bring reliable, off-chain data to internal, on-chain environments. When a blockchain network is unable to receive this data to allow it to operate correctly, it is known as the oracle problem.