Topics are typically set up by an instructor before a course. As seen below, when you Pin you can select a topic for the Pin. Depending on instructor settings you may be prompted or required to add a topic.
Topics allow you to more easily find or filter to only view specific information. For example, if there is a Topic called "Chapter 2" and Pins are marked with that Topic, it will be easy to study content related to Chapter 2 by selecting that topic. Topics can be selected as filters by clicking on "Trending Topics" on the righthand sidebar. Those "Trending Topics" are the ones that have seen the most activity over the past week. Clicking "Show all Topics" beneath that will expand to the full topic list so that you can filter by any topic that has been set up for your board.
Clicking on the topic will make the feed so that it only displays the selected Topic(s). To remove these Filters, click on the X on the topic names that appear near the top of the feed.
Students and other learners (i.e., "board followers") cannot create Topics, only instructors and other course administrators can. Therefore, if you feel a Topic may be useful you can suggest it to the instructor or you can use #hashtags to organize or flag specific content. You can also bookmark any Pins that you want to be able to keep up with.