Training data refers to the collection of information used to teach machine learning models how to make predictions or decisions. This data can include various types of content, such as text, images, or numerical values, and is essential for the model to learn patterns and relationships within the data. The quality and quantity of training data directly impact the model's performance and accuracy. In the context of artificial intelligence, algorithms analyze the training data to identify trends and features. Once trained, the model can then apply its learned knowledge to new, unseen data, enabling applications in areas like natural language processing and computer vision.