Tags (also knowns as labels, related to hashtags) are the modern approach to organizing saved objects. These objects can be anything from a general software perspective, including files or images. In Ada, the objects we are concerned with organizing include items, assets, tests, examinees, and sessions. To do this, we use tags.
A tag, of course, is a way of labeling an object. A photo your and friends in Chicago during 2019 might be tagged as Chicago, 2019, and Friends (though automated image recognition software might tag it with things like Cars, Stoplights, People, and Streets). It's important to note that these are orthogonal - unrelated to each other, and not in a strict hierarchy.
An examinee in Ada might be tagged as Hispanic (Ethnicity), Reduced Lunch (Lunch Status), English Language Learner (Language Status), and attending Jackson High School, for example. Again, these are orthogonal, as a student's Ethnicity does not tell you which High School they attend.
Tags have a number of advantages over the traditional folder-based system. For one thing, it provides more and better data to use in searching or reporting. For example, if you wanted to create a report that analyzed the average test score in each High School, broken down by the Ethnicity of each student, this is quite easy to do. It also makes it easier to search and find, such as filtering a list of all examinees by Ethnicity.