A mining pool is a group of miners who combined their computational resources over a network to strengthen the probability of finding a block or otherwise successfully mining for cryptocurrency.
In other words they are like working in a group instead of doing it alone. People do say that the more the better. The more hashing power a mining pool has, the better its chances of mining a block
According to bitpanda: the chart above shows how the current balance of power across the Bitcoin mining space plays out. Note that each of those pools usually consists of thousands of individual miners from across the world. The exact number of individual computers contributing to the network is hard to tell, but according to an estimate a Quora user calculated based on performance in May 2019, there are around 3,800,000 (3 million and 800 thousand) machines involved around the globe.
You can see in the graph that bitcoin mining is not really that decentralized as most mining percentage comes from organized mining pools. Still, as long as the distribution of hashing power is reasonable and individual pools remain well below running 51% of the network, this is good news.
