What is the difference between supervised and unsupervised learning?

**Supervised learning** — model learns from labelled data (input → output pairs)
- Examples: Linear regression, Random Forest, SVM
- Use case: Predicting house prices, spam detection

**Unsupervised learning** — model finds patterns in unlabelled data
- Examples: K-Means clustering, PCA, Autoencoders
- Use case: Customer segmentation, anomaly detection

**Semi-supervised** combines both.