Working on a large project, you often need to create the lists of tasks, and keep your team mates informed about the issues that require their attention. Such issues can include the questions that should be answered, certain changes that should be done later, areas of optimization and improvement etc.
CLion suggests to use special TODO comments in the source code. Such comments can be used in all supported file types, and should match a certain TODO pattern. CLion comes with one pre-defined pattern, but you can define as many TODO patterns as required. When a matching occurrence is encountered, it is interpreted as a TODO item. CLion highlights such comments in accordance with the Color Scheme settings.