Text annotation is identifying and labeling sentences with additional information or meta data to define the characteristics of sentences. This information could be highlighting parts of speech in a sentence, grammar syntax, keywords, phrases, emotions, sarcasm, sentiments and more depending on the scope of a project. Machine learning modules are fed with such AI training data, where they learn diverse aspects of sentences, sentence formation, and more to understand human conversations better. As they learn with properly annotated data, they become better at mimicking human conversations (current virtual assistants). However, feed them with poorly annotated data, and you will find them deliver irrelevant, dumb, or misleading responses. That’s why text labeling should be done by experts, who meticulously tag every single aspect of a sentence to ensure nothing crucial for machines to understand and learn is overlooked. "