My understanding is that it’s basically like a normal pool, in that it provides the necessary communication between a full Bitcoin node and your miner itself to build block templates. However, instead of pooling resources with others and sharing rewards, if you mine a block, you keep all of the rewards (less the pool fee).

As I understand it, there is some complexity involved with running your own miner and configuring it against your own full node; but honestly I’ve never tried it or looked that far into.