Intent detection
Intent detection is the step in which a conversational system works out what the caller is trying to achieve (book, cancel, ask about an order, reach a person) from the words they used.
Also called: intent recognition, intent classification
Callers rarely announce their intent in the form a system expects. "I was in last week and the thing you fitted is making a noise again" is a complaint, a request for a repair visit, and possibly a warranty question. Intent detection maps that to something the system can act on.
Older systems used a fixed list of intents with trained classifiers, and anything outside the list fell into a catch-all. Language-model-based agents infer intent more flexibly and can hold several at once, but the concept is the same: the conversation only becomes useful once the system knows what the caller wants.
For routing, intent is what replaces the menu. Instead of "press 2 for billing", the agent asks what the caller needs and sends them, or their message, to the right place, which is only as good as the detection behind it.