miners are rewarded new bitcoins every 10 minutes.
The role of miners is to secure the network and to process every Bitcoin transaction.
Miners achieve this by solving a computational problem which allows them to chain together blocks of transactions (hence Bitcoin’s famous “blockchain”).
For this service, miners are rewarded with newly-created Bitcoins and transaction fees.

The issuance rate is set in the code, so miners cannot cheat the system or create bitcoins out of thin air. They have to use their computing power to generate new bitcoins.