Some people are mighty curious and are prone to enquire about other people. This can happen on a date, when you get asked about previous dating experiences or relationships (perhaps you were engaged or married previously).
It is strongly recommended that you studiously avoid discussing past dates or relationships. You will be tempted to say negative things to make your current date feel better about themselves, dragging you into a bad place. Or you will say something positive and this will not always be well-received.
Your date may seem to want to know, but they most likely cannot handle it. If your date asks you whether you dated a particular person or about something a previous date had said, you should politely avoid talking about it.