Machine learning is a method that allows computers to learn from examples.
Instead of programming every rule manually, the computer is shown many examples. From these examples it learns patterns and relationships.
For example, a computer might see many pictures of cats and dogs. Over time it learns the differences between them.
When it later receives a new image, it can estimate whether the picture shows a cat or a dog.
Machine learning can therefore be seen as training for computer programs. The more examples they receive, the better they become at certain tasks.