A Bitcoin mining pool hash rate is a measure of the combined computing power of all the miners in a given mining pool. It is calculated by taking the total number of hashes that the pool is capable of producing in a given second and dividing it by the total number of miners in the pool. This number is then expressed as a hash rate, usually measured in hashes per second (H/s).

The higher the hash rate, the more computing power the pool has and the more likely it is to successfully mine a block of transactions. When miners join a mining pool, they are contributing their individual computing power to the collective computing power of the pool. The hash rate of the pool is a measure of the combined computing power of all the participants.

It is important to note that the hash rate of a mining pool does not necessarily indicate the number of blocks it will mine. This is because the difficulty of mining a block is constantly changing. The difficulty is adjusted by the network in order to ensure that the average time between blocks mined is 10 minutes. The higher the hash rate of the pool, the more likely it is that it will be able to successfully mine a block before the difficulty increases.

In addition, the hash rate of a mining pool is also an indication of its profitability. The higher the hash rate, the more likely it is that the pool will find a block before another pool and receive the block reward. The block reward is currently 12.5 BTC per block. Therefore, a pool with a higher hash rate is more likely to be more profitable in the long run.