Too Long; Didn't Read
When bitcoin began to gain momentum and people got opened to the concept of mining, many woke up to it setting up their own little mining rigs at their place of convenience. But as difficulty increased, it became unprofitable to privately run a mining rig. Then came cloud mining. Cloud mining is basically buying a contract from a commercial scale mining rig. These are companies that go the extra mile to optimize operations to incur the minimum cost possible and produce at the optimum. They offer contracts to everyday people where hashpower is sold. The people who bought this contract will be paid yields according to the hashpower they got with some deductions based on the contract terms (for maintenance, energy, cooling, etc).