Machine learning is a branch of artificial intelligence in which computers derive patterns from data instead of having every rule explicitly programmed. Depending on the task, models learn from labelled examples (supervised), from unlabelled data (unsupervised) or through rewards (reinforcement). Applications range from spam filters and demand forecasts to product recommendations. Quality depends heavily on the quantity and quality of the training data.
Deep learning is a branch of machine learning that uses artificial neural networks with many layers. Such networks learn from large amounts of data which features matter – from edges in images to relationships of meaning in texts. Deep learning underpins today's language models, image and speech recognition and machine translation, and usually requires considerable computing power and training data.
In supervised learning, a model learns from examples for which the correct answer is already known, such as emails labelled “spam” or “not spam”. From these it derives rules to classify new, unseen cases or to predict values. Typical tasks are classification and regression; most of the effort goes into creating cleanly labelled data.
In unsupervised learning, a model receives data without predefined correct answers and searches for structures on its own. Typical methods are clustering, which groups similar records, and dimensionality reduction, which condenses many features into a few essential ones. Organisations use it to discover customer segments or spot unusual transactions; the groups found must then be interpreted by domain experts.
Reinforcement learning is a branch of machine learning in which an agent learns by trial and error. It acts within an environment, receives rewards for good outcomes and penalties for bad ones, and in this way develops a strategy that maximises its overall reward. Well-known examples include programs that master board games such as Go, robot control and the fine-tuning of language models based on human ratings.
