What are tags and tag sets?
Tags are labels you attach to questions — by topic, skill, difficulty, learning objective, or anything else you need to organise by. A tag set groups tags along one dimension, so a single question can be classified across several dimensions at once (its subject and its skill and its difficulty, for example).
Good tagging is what makes a question bank usable at scale: it powers exam blueprinting, targeted practice, and rich analytics that break performance down by any tag. Synap's tagging system is extensively used in the medical field — see OSCEs and clinical assessments.