There are many types of speech recognition. Typically speech recognition starts with the digital sampling of speech. The next stage is acoustic signal processing. The next stage is recognition of phonemes, groups of phonemes and words. HMM-based systems are currently the most commonly used and most successful approach.
Most systems utilise some knowledge of the language to aid the recognition process.
That is, they try to convert the words into a representation of what the speaker intended to mean or achieve by what they said. Back to Section 6 of the comp.speech FAQ Home Page .