HMM contains two types of states: observable and hidden. Let $\{ h_1,h_2,h_3,\cdots,h_n\}$ be hidden states and $\{o_1,o_2,o_3,\cdots, o_m\}$ be the observable states.
Suppose the $n^2$ transition probabilities $p(h_j|h_i)$ and the $mn$ emission probabilities $p(o_j/h_j)$ are given along with the initial probability distribution vector $\pi =[\pi_1, \pi_2, \pi_3, \cdots, \pi_n]$
Then what is meant by decoding in HMM?