Mining Pool
Mining pools may contain hundreds or thousands of miners using specialized protocols. In all these schemes B stands for a block reward minus pool fee and p is a probability of finding a block in a share attempt (p = 1/D, where D is current block difficulty). A pool can support "variable share difficulty" feature, which means that a miner can select the share target (the lower bound of share difficulty) on his own and change p accordingly. The list of pools for mining is extensive – in the world there are more than a thousand. The vast majority of users work through bitcoin pools. The level of complexity of the production of this currency is so high that alone, even with a supercomputer profit is not obtained. Therefore, all new pools are formed. There are other cryptocurrencies, younger than bitcoin, which are faster and easier to mine. But they do not have real value in the network, and they can only earn with the hope that in the future their rate will grow, and this is more like speculative mining.