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# computing smoothed values.
The forward and backward steps are often called "forward message pass" and "backward message pass". The wording originates from the way the algorithm processes the given observation sequence. First the algorithm moves forward starting with the first observation in the sequence and going to the last, and then returning back to the first. At each single observation in the sequence, probabilities to be used for calculations at the next observation are computed. During the backward pass the algorithm simultaneously performs the smoothing step. This step allows the algorithm to take into account any past observations of output for computing more accurate results.
The forward-backward algorithm can be used to find the most likely state for any point in time. It cannot, however, be used to find the most likely sequence of states (see [[Viterbi algorithm]]).
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