Andrey Markov was a famous mathematician from Russia. He created a system of mathematics called Markov Chains that helps us predict what will happen in certain situations. Markov Chains can be used to make predictions about things like the weather, stock prices, and sports games. Basically, Markov Chains look at how one event can impact a sequence of events. For example, if it's raining in one place, it's more likely to be raining in the next place too. So, if you know that one event will happen, then you can use this type of mathematics to figure out what will happen next.