Although I generally agree with what @Kryztoval said, there is a small clarifying to be done there.
Oracles are a means of providing real life external data inside the blockchain for Contracts to use. This does not have much to do with mining itself except that miners have to include the various Oracle’s transaction types in micro blocks.
What is more interesting there - Oracles are services, so providers of those services are to be paid for their work. Every Oracle provider specifies the (minimal) price they are to get for answering a query asked to their own Oracle. So you are getting paid for answering questions, if other users expect you to provide a correct answer. This is providing decentralization of information flow as well. You also don’t have to trust an Oracle - you can specify in your smart contract that expects an Oracle response, a list of Oracle providers to be used and later on you can build a consesus of their responses.
Imagine you have a smart contract in which you’re getting paid of the temperature outside falls bellow 10C. You need a source of information and Oracles provide exactly this. Supposedly you don’t want to trust one single Oracle, but rather specify three different ones - OracleA, OracleB, OracleC that provide temperature outside. You ask them, they respond:
- OracleA - 9C
- OracleB - 11C
- OracleC - 8C
So now you can use those results in your smart contract and having 2 out 3 bellow 10 - means you can safely execute your contract in a decentralized and trustless manner.