A State is said to be Markov if the Markove property holds:

\[\mathbb{P}[S_{t+1} | S_t] = \mathbb{P}[S_{t+1} | S_1, \dots, S_t]\]

This formula encapsulates the idea that **the future is independent of the past given the present**. This is pretty powerful idea since all the prior state information except for the present is needed.