Machine learning can be divided into three main categories: supervised learning, unsupervised learning, and reinforcement learning. Each type uses data differently and is suited to different types of problems.

Supervised learning relies on labeled data, where each example in the dataset includes both the input and the correct output. The goal is to learn a mapping from inputs to outputs, so you can predict the output for new, unseen data. Unsupervised learning works with unlabeled data, where only the inputs are given, and the task is to find patterns or structure in the data without explicit answers. Reinforcement learning is different: an agent learns to make decisions by interacting with an environment, receiving feedback in the form of rewards or penalties, and improving its strategy over time based on this feedback.

The key distinction between these types lies in the presence of labels and the way feedback is provided. Supervised learning uses direct examples of correct answers, unsupervised learning finds structure with no answers provided, and reinforcement learning relies on trial and error with feedback from the environment.

To understand which problems are best suited for each type of machine learning, consider the structure of datasets you might encounter. If you have a dataset of house prices where each row contains features like the number of bedrooms, location, and the actual sale price, this is labeled data, making it ideal for supervised learning — your goal could be to predict the price of a house given its features. If you have a dataset with only customer transaction histories and no information about customer segments, you might use unsupervised learning to discover groups of similar customers. For reinforcement learning, imagine a robot learning to navigate a maze: the robot receives a reward for reaching the exit and must learn the best sequence of moves through trial and error, without being told the correct path in advance. The structure of the dataset — whether it contains labels, lacks them, or provides feedback through rewards — determines the most suitable machine learning approach.