What does being "discrete" (or "discreet") mean?

It basically means that in some aspects of there life, if not all they havent come out yet, so while at home they might be all over you, but in public they will act as a friend, especially if someone they know is around. Being in a relationship like that can be kinda stressful but if you hang in there and stay by there side till they are ready to come out it will be very rewarding in the long run. Only other option as to why is that they may be currious and later on realize that it isnt for them and dont want to be known as gay/bi by friends or family