ETH is a cryptocurrency that can be mined by using GPUs. Those GPUs are active 24/7 in solving math calculations, and you get rewarded for solving them. Your earnings will be based on your mining power. If you want to get more earnings, you need to increase the amount of GPUs. The network difficulty increases depending on how many GPUs are mining, making it harder to mine. You can update or add more GPUs in order to keep your earnings.