Data annotation is the process of labeling data to make it understandable for machines. It involves tagging, categorizing, or marking data points with relevant metadata, such as keywords, descriptors, or attributes. Annotation is crucial for training machine learning models, as it provides the necessary context and structure for algorithms to learn patterns and make accurate predictions. Common types of data annotation include image labeling, text tagging, audio transcription, and video segmentation. High-quality annotation is essential for ensuring the accuracy and reliability of AI systems across various applications, including autonomous vehicles, natural language processing, healthcare diagnostics, and more. Efficient annotation methodologies and tools are continually evolving to meet the increasing demands of data-driven technologies.