Mining means registering keys on subnets to actively serve the requests of subnet validators with outputs in competition with other miners to maximize rewards. Perpetually optimizing for the evaluation system applied by validators.
Miners are endpoints tied to a onchain identifier, all systems used to produce the miner's output are offchain and unconstrained in their complexity and approach. This leaves full freedom to creatively solve the problems defined by validators.
The work and required skillset of a miner is unique to the validation methodology of each subnet.