Optimization means getting the same result (or a better one) using fewer resources.

Energy efficiency
In mining, one of the most important things to optimize is energy efficiency.
Energy efficiency tells you how much power (electricity) you use to produce a certain amount of hashrate.

It is usually measured in:
W/TH (watts per terahash)

Watt (W): unit of power consumption (how much electricity the device uses)
Terahash (TH/s): how many trillions of hashes the device calculates every second

Example

ASIC 1: 10 TH/s, 200 W. Efficiency = 200 ÷ 10 = 20 W/TH

ASIC 2: 15 TH/s, 450 W. Efficiency = 450 ÷ 15 = 30 W/TH

Even if the second ASIC is more powerful, it is less efficient because it consumes more energy for each TH.
Conclusion: The lower the W/TH value, the better the efficiency.


How to optimize mining

Here are some practical ways to improve efficiency:
Better hardware: newer or higher-quality devices usually have lower W/TH
Cooling: keeping hardware cool improves performance and reduces energy waste
Undervolt: lowering voltage to reduce power consumption while keeping similar performance
Mining software: choosing efficient software with low overhead and low dev fees
Mining pool: selecting pools with lower fees to keep more of your rewards

Optimization is basically about this: maximize hashrate, minimize costs (especially electricity)