In simple terms, blockchain oracles are solutions that provide blockchains with off-chain information. Blockchains are rather cut-off from the outside world in that regard. Protocols may need certain off-chain information or events. After all, trading, as any other economic activity, relies on relevant and accurate information to work. Blockchain oracles fulfill that need.
Oracles provide that lifeline between the blockchain and the off-chain information.
It is importnant to note that blockchain oracles are not sources of data. They are relays that verify and authenticate off-chain information so that on-chain services could access and use it. The data itself comes in a variety of forms, from the information about transaction completion to the change in asset’s price. Some types of oracles are not limited to relaying that information to the blockchain, but can also send it back to off-chain as well.
There are many types of blockchain oracles on the crypto market. Some are specialized hardware pieces, others are entirely software, and despite their common goal, each type has its own unique trait.
Haven currently utilises Chainlink for feeding the necessary data to the network. More details on Chainlink can be found here