Imagine a market where two apple vendors are selling apples. Each of them has their own reserves of apples and their own demand in the market. Let’s say both vendors have an inventory of 100 apples but 100 people are waiting in queue to buy from the first vendor and only 30 people are waiting in queue to buy from the second vendor, the first vendor can sell at a higher price. In such a scenario, the 100 people in the queue for the first vendor will eventually get to know about the second vendor in the market and instead of waiting in the line, some will move to the second vendor to buy apples.  With this increase in the demand, the second vendor will increase the prices and eventually the businesses of the two vendors will come to an equilibrium. That's maybe similar to Bitcoin's price in different areas.