Machine learning is part of AI which is part of computer science. It is a field of study concerned with the development of statistical algorithms that can learn from data and generalize to unseen data.
We can make distinction between supervised and unsupervised machine learning. The former uses labeled datasets to train algorithms to predict those labels while the latter learns patterns exclusively from unlabeled data. Semi-supervised learning combines both labeled and unlabeled data for training.
Lastly, reinforcement learning is a third machine learning technique that learns through trial and error using feedback from its actions.
When talking about machine-learning we usually refer to the algorithm utilizing neural-networks. Neural-networks learn via a process inspired by the human brain. Different types of neural-networks exist and algorithms other than neural-networks also exist.
Natural language processing enables a computer system via machine-learning to understand and generate human language in text format or spoken words. Computer vision enables a computer system via machine-learning to identify and understand objects and people in images and videos.
Here is a course that overviews machine-learning and its application in AWS cloud.