"Please tell me about yourself" is actually not a question, but an imperative sentence, or a command. "How would you describe your symptoms?" is an open question. An open question is one that requires more thought instead of a simple yes or no. It could also be a funneling question, where it starts with one open sentence and follows with other questions that are gradually more restrictive. For instance, someone could ask you how you would describe your symptoms, then ask how long you've had them, and then ask how long those symptoms lasting in that time period.