The Bitcoin network is designed to produce a certain number of new Bitcoins every 10 minutes. In order to ensure this, Bitcoin miners verify transactions and add them to the block they are working on. For their work, they earn fees paid by the users of the Bitcoin network. When a new block is created, it is added to the end of the blockchain and a reward is given to the miner.
The reward currently stands at 12.5 Bitcoins but will halve every 210,000 blocks (roughly every 4 years). While it may seem like the miners are in control, they are actually at the mercy of the protocol. The protocol cannot be changed without the consent of nearly all miners as they would then be creating invalid blocks.
The only way to earn Bitcoin is through mining or by purchasing it on an exchange. There is no other way to earn Bitcoin. Mining is how new Bitcoin is created and transactions are verified on the network. Miners are rewarded with Bitcoin for their work verifying transactions.
Purchasing Bitcoin on an exchange is the only other way to get Bitcoin. You will need to use fiat currency (USD, EUR, etc.) to buy Bitcoin on an exchange.