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What is a chatbot? Rules, NLU, and LLMs

A chatbot is a system that converses with a user in text or voice to answer, guide, or perform an action. It may be rule-based, NLU-based, or powered by a large language model. The NIST AI RMF and OWASP LLM Top 10 stress that a public-facing bot must manage risk, hallucinations, and prompt injection.

In one sentence

A chatbot automates conversation to help, qualify, or route users.

Key points

  • Three families: scripts/rules, classic NLU, generative LLMs.
  • Success is resolution, support deflection, and satisfaction—not “wow”.
  • Clear human escalation and content guardrails are required.
  • Conversation logs are personal data to protect.

Term at a glance

Chatbot
Conversational agent · Dialogue bot
English term
Chatbot
Domain
Artificial intelligence
Category
Assistants
Level
Beginner to intermediate

What does “chatbot” mean exactly?

Early bots followed decision trees. NLU platforms (e.g. Dialogflow) added intents and entities. LLMs enable more flexible answers at the cost of harder control.

A chatbot is not “AI” by magic: without a fresh knowledge base, tools (APIs), and refusal policies, it invents or blocks.

For an SME, the winning case is often FAQ + booking + lead qualification, with handoff to a human.

How do you deploy a useful chatbot?

  1. 01

    Pick priority intents

    Top 10 real support/sales requests.

  2. 02

    Connect sources and tools

    Validated FAQ, CRM, calendar—not only generated text.

  3. 03

    Secure

    Control prompts, filter PII, log, limit sensitive actions.

  4. 04

    Measure and improve

    Resolution rate, abandonment, CSAT, review failed chats.

A concrete chatbot example

A dental clinic in Laval deploys a site bot: emergencies vs planned care, available slots, document reminders. Complex cases escalate to reception. In two months, 35% of after-hours bookings go through the bot, without raising triage errors thanks to strict symptom rules.

What are chatbots used for?

Tier-1 support

FAQ, order tracking, ticket status.

Sales qualification

Budget, need, urgency before an advisor.

Appointment booking

Slots and automatic reminders.

Internal assistance

HR, IT, procedures for employees.

Benefits and limits of chatbots

  • 24/7 availability
  • Deflects repetitive tickets
  • Structured data capture
  • Scalable first contact
  • Hallucinations if LLM is poorly framed
  • Frustration if escalation is opaque
  • Knowledge maintenance cost
  • Security risks (prompt injection, data leaks)

How does a rule-based bot differ from an LLM bot?

ChatbotGenerative LLM chatbot
FlexibilityLow outside scriptsHigh across phrasings
ControlStrong and predictableNeeds guardrails
MaintenanceTrees to updatePrompts, RAG, evals
RiskMissing answersFabrications / leaks

Why chatbots matter for Quebec SMEs

Support and leads do not wait for office hours. A well-bounded bot cuts repetitive load and captures after-hours demand—without pretending to replace experts on high-risk topics.

Frequently asked questions

Do we need an LLM for a chatbot?

No. Many FAQs are better with controlled flows + document search.

How do we avoid hallucinations?

Ground answers (RAG), ban out-of-scope topics, test with evaluation sets.

Does the bot replace agents?

It absorbs the repetitive; complex and relational cases stay human.

What about privacy (Law 25)?

Inform users, minimize data, secure logs, define retention.

Related terms

Sources and references

Want a bot that actually resolves requests? We frame intents, sources, and guardrails for your service.

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