You can create text information if you want to provide supplementary information that relates to several questions. It is useful to create text information if you have several questions that need to reference the same passage and you want to avoid repeatedly writing the same text for each question.
For example, perhaps you have a case study you want to base several questions on. Instead of inserting the case study into each question, you can simply create a text information item and have your related questions appear directly underneath it.