Ideas into intelligence.
A practical introduction to AI, machine learning and the systems that bring models to life. Open a lesson, follow an example and test your understanding.

Understand. Experiment. Build.
A visual reference for AI, machine learning and practical model engineering. Open any topic to read a concise explanation.
01 / FOUNDATIONSWhat is AI
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Artificial intelligence builds systems that perform tasks associated with human intelligence, including perception, reasoning, language generation and decision support.
02 / FOUNDATIONSWhat is ML
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Machine learning is an approach to AI where a model learns patterns from examples and applies them to new data.
03 / LANGUAGEWhat is an LLM
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A large language model learns statistical relationships in text, represents text as tokens and predicts useful continuations from context.
04 / LANGUAGEHow LLMs work
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An LLM converts input into tokens, processes them through transformer layers and generates output one token at a time.
05 / METHODSMachine learning methods
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Supervised, unsupervised, semi-supervised and reinforcement learning address different data and feedback settings.
06 / GENERALIZATIONOverfitting and underfitting
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Overfitting memorizes training examples; underfitting is too simple to capture useful patterns. Data, capacity and regularization help balance both.
07 / GENERALIZATIONBias–variance tradeoff
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Bias comes from overly simple assumptions; variance comes from sensitivity to the training sample. Good validation balances both.
08 / TRAININGParameters vs hyperparameters
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Parameters are learned from data. Hyperparameters are chosen around training, such as depth, batch size and regularization strength.
09 / DATAHandling missing values
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Measure where values are missing and why, then use a meaningful default, imputation, an indicator or a model that supports missing values.
10 / DATADetecting and handling outliers
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Use domain limits, robust statistics, IQR, z-scores and visual checks. Investigate causes before removing, capping, transforming or retaining outliers.
11 / EVALUATIONConfusion matrix
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A confusion matrix counts true positives, true negatives, false positives and false negatives, revealing which classes a classifier confuses.
12 / FEATURESFeature selection
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Feature selection keeps useful inputs and removes noisy, redundant or unavailable signals using domain knowledge and model-based checks.
13 / DATA QUALITYData leakage and prevention
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Leakage uses information unavailable at prediction time. Split data before fitting transformations and keep future information out of features.
14 / CLASSIFICATIONLogistic regression
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Logistic regression estimates class probabilities from weighted features. A threshold converts probability into a decision.
15 / ENSEMBLESRandom forest
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A random forest combines decision trees trained on varied samples and feature subsets, reducing variance and providing a strong baseline.
16 / ENSEMBLESBagging vs boosting
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Bagging trains models independently and aggregates them. Boosting trains sequentially so later models focus on errors.
17 / ENSEMBLESXGBoost vs random forest
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Random forests are robust and easy to tune. XGBoost builds regularized trees sequentially and can achieve excellent tabular accuracy with careful tuning.
18 / EVALUATIONF1 score
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F1 is the harmonic mean of precision and recall when both false positives and false negatives matter.
19 / EVALUATIONROC–AUC
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ROC–AUC summarizes ranking across classification thresholds. Precision–recall analysis can be more informative for highly imbalanced data.
20 / EVALUATIONAccuracy, precision and recall
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Accuracy suits balanced classes. Precision matters when false positives cost more; recall matters when missing a positive case costs more.
21 / VALIDATIONCross-validation
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Cross-validation rotates training and validation folds to provide a more stable estimate for model comparison.
22 / GENERALIZATIONRegularization
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L1, L2 and dropout discourage overly complex models. Their strength is controlled by a hyperparameter.
23 / OPTIMIZATIONLearning rate
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The learning rate controls how far an optimizer moves parameters after each update. Too high overshoots; too low slows training.
24 / OPTIMIZATIONHyperparameter tuning
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Tuning compares configurations using validation, exploring depth, learning rate, regularization and batch size.
25 / DIMENSIONALITYPCA
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Principal component analysis projects correlated features into fewer directions that explain much of the variance.
26 / ENGINEERINGML pipeline
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An ML pipeline makes preparation, feature creation, training, evaluation and serving repeatable and consistent.
27 / OPERATIONSMLOps
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MLOps combines ML, engineering and operations practices for versioning, testing, deployment, monitoring and retraining.
28 / OPERATIONSModel drift
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Model drift is a decline in usefulness as incoming data, behavior or input–outcome relationships change.
29 / LIFECYCLEEnd-to-end ML project lifecycle
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A typical lifecycle moves from framing and data collection through labeling, features, training, validation, deployment, monitoring and iteration.
Training or inference?
A model uses its learned weights to process a new input. Which stage is this?
Choose an answer to see the explanation.