Now that you know what Bitcoin mining is, you might be thinking, “Cool! Free money! Where do I sign up?” Well, not so fast…
Satoshi Nakamoto, who invented Bitcoin, crafted the rules for mining in a way that the more mining power the network has, the harder it is to guess the answer to the mining math problem. So the difficulty of the mining process is actually self-adjusting to the accumulated mining power the network possesses.
If more miners join, it will get harder to solve the problem; if many of them drop off, it will get easier. This is known as mining difficulty.
Why on earth did Satoshi do this?
Well, he wanted to create a steady flow of new bitcoins into the system. In a sense, this was done to keep inflation in check. Mining difficulty is set so that, on average, a new block will be added every ten minutes (i.e., the number will be guessed every ten minutes on average).
Now, remember, this is on average. We can have two blocks being added minute after minute and then wait an hour for the next block. In the long run, this will even out to ten minutes on average.
As you can imagine, this type of self-adjusting mechanism has created a sort of “arms race” to get the most efficient and powerful miners as soon as possible.