What are CPU threads?

Each processor can concurrently perform several operations, which is called multithreading. A modern CPU can have from 2 to 30+ cores.

A core is a hardware processor unit that can split its performance into multiple threads (virtual cores), and thus carry out multiple coherent tasks at the same time.

So, the more cores (threads) you have, the faster your CPU works, the higher the mining speed is, and the more BTC you earn.