Adding mark-up, basically. Examples for text data: topic tags, marking mentions of companies, finding descriptions of protein interactions. For images people m

Adding mark-up, basically. Examples for text data: topic tags, marking mentions of companies, finding descriptions of protein interactions. For images people mostly do segmentation (finding object boundaries) and classification. If the model is generating images or text, you usually need to do annotation to evaluate the model. For instance, you need to know whether the translations are grammatical, whether an image is coloured correctly, etc.