The hierarchy: AI, ML, DL, GenAI, Agentic AI
Artificial Intelligence (AI) is the broadest term: any technique that lets a computer mimic human-like intelligence. AI is a category, not a specific technology — hand-coded rule systems and modern chatbots both count.
Machine Learning (ML) is a subset of AI: instead of hand-written rules, the system learns patterns from examples. The output is a model — a function shaped by data. Shaping it is training; using the finished model on new data is inferencing.
An algorithm is the general method used to train a model (e.g., linear regression, gradient boosting). The model is the specific trained artifact produced by applying an algorithm to data.
Deep Learning (DL) is a subset of ML using neural networks — layered structures loosely inspired by neurons. It powers computer vision (interpreting images/video) and NLP — Natural Language Processing (understanding/generating human language).
Generative AI (GenAI) is a subset of deep learning: models sophisticated enough to generate new content rather than just classify or predict a number. The engines behind most GenAI are Large Language Models (LLMs) — deep learning models trained on huge text corpora that predict 'what comes next' well enough to write, answer, and converse.
Agentic AI is NOT nested inside GenAI — it's drawn as a connected box. It's a GenAI model wrapped with tools, memory, and multi-step planning: given a goal, it plans, acts, observes, and adjusts across multiple steps autonomously.
Bias, fairness, fit
- Bias — systematic skew in predictions, often from unrepresentative training data.
- Fairness — the broader goal that outcomes don't unfairly disadvantage particular groups.
- Overfitting — model memorized training noise; great on training data, poor on new data.
- Underfitting — model never learned the pattern; poor on both.
The three learning types
- Supervised learning — trained on labeled data (every example has the correct answer attached).
- Unsupervised learning — no labels at all; finds structure/groups on its own (e.g., clustering).
- Reinforcement learning — no fixed dataset; an agent takes actions and learns from reward/penalty feedback over time (later refined via RLHF — Reinforcement Learning from Human Feedback for LLMs).
Data types
Labeled vs. unlabeled; structured/tabular (rows and columns) vs. unstructured (images, audio, free text); time-series (sequential, order matters — e.g., IoT sensor data, GPS pings).
Data type, learning type, technique, and inferencing type are independent axes the exam tests separately — don't assume one implies another.
Types of inferencing
- Batch — many inputs processed together on a schedule, nobody waiting live.
- Real-time — single request, instant response, someone waiting live.
- Asynchronous — single request submitted, response delivered later.
- Serverless — an infrastructure/billing classification (no servers to manage, pay per use, scales to zero when idle) — independent from the timing classifications above.
Algorithm examples: Linear Regression vs. Gradient Boosting
Linear regression fits one straight line through a scatter of data points, minimizing overall distance to all of them. Simple, fast, highly explainable — used for regression problems (predicting a continuous number). AWS SageMaker built-in: Linear Learner.
Gradient boosting builds many small decision trees in sequence — each new tree corrects the residual errors of the previous ones; the final prediction combines them all. More accurate on complex tabular data, less explainable. AWS SageMaker built-in: XGBoost.
The customer-support email story (same task, five eras)
- AI — hand-written if/then rules, no learning at all.
- ML — a spam classifier trained on thousands of labeled emails (supervised learning).
- Deep Learning — a neural net reads the full email and catches nuance/tone a shallow model misses.
- GenAI — an LLM drafts a full personalized reply from scratch (creating text, not picking a label).
- Agentic AI — the system checks the order database, drafts, and sends the reply autonomously, planning multiple steps without being told each one.