Hidden Markov Model HMM is a probabilistic model of time series, which describes the process of generating a random sequence of unobservable states randomly generated by a hidden Markov chain, and then generating an observable and observed random sequence from each state.

Hidden Markov Model is a statistical model that is used to describe a Markov process with hidden unknown parameters. The difficulty is to determine the hidden parameters of the process based on observable parameters, and then use these parameters for further analysis, such as pattern recognition.