where you are reborn into. heaven, hell, animal, human, ghost. What is this about? Is this just a possible belief/concept, or did Buddha teach this?
Yes, the Buddha taught that living beings (and we humans are living beings) are born into conditions dependent on past causes, and after death with the dissolution of the body, move on to better or worse conditions dependent on causes made in this lifetime.
However, life, which is inherent in and gives rise to all living beings, never came into existence at some time in the past nor will it cease to exist in the future. Your life, which is in no way separate from or something other than the life of all living beings, never started. It will never end.
I've never been able to wholly make this a part of myself, and if I ever do I imagine I will have won and no longer have to suffer, but I find that I can relate to it and make use of it through contemplation.