Buddha is a great enlightened teacher who selflessly shared what he knew to all, regardless of caste and gender. He was far ahead in his times. Today his teachings on rebirths are validated by many who went through near-death experiences or deep meditation. Buddha spent 45 years of his life teaching on the path to nirvana.
He encouraged us to be deep thinkers; to question and verify even his teaching before accepting his teaching. Even though I was born in a Buddhist/Taoist family, I only throughly accept his teachings last year after reading from other sources like the near-death experience website and books written by Anita Moojani. What they shared was already revealed by the Buddha more than 2500 years ago. We are the heirs of our karma. Buddha could only show the path, but it is only through practice that one could end endless samsara cycle.
Buddha said that with desire and craving, we went through endless cycles of rebirths in one of the six realms: hell, hungry ghost, animals, human beings, asura and heavenly realms.
From Wikipedia
Tradition ascribes to the Buddha himself instruction on how to pay him homage. Just before he died, he saw his faithful attendant Ananda, weeping. The Buddha advised him not to weep, but to understand the universal law that all compounded things (including even his own body) must disintegrate. He advised everyone not to cry over the disintegration of the physical body but to regard his teachings (The Dhamma) as their teacher from then on, because only the Dhamma truth is eternal and not subject to the law of change. He also stressed that the way to pay homage to him was not merely by offering flowers, incense, and lights, but by truly and sincerely striving to follow his teachings. This is how Buddhists are expected to celebrate Vesak: to use the opportunity to reiterate their determination to lead noble lives, to develop their minds, to practise loving-kindness and to bring peace and harmony to humanity.
The Triple Gem (https://www.buddhanet.net/e-learning/pathmaps.htm)
1. The Buddha — The self awakened one. The original nature of the Heart;
2. The Dhamma — The Teaching. The nature of reality;
3. The Sangha — a. The Awakened Community. b. Any harmonious assembly. c. All Beings.
The Four Noble Truths
1. The Noble Truth of Dukkha (Suffering) - stress, unsatisfactoriness, suffering;
2. The Noble Truth of the causal arising of Dukkha, which is grasping, clinging and wanting;
3. The Noble Truth of Nirvana, The ending of Dukkha. Awakening, Enlightenment. "Mind like fire unbound";
4. The Noble Truth of the Path leading to Nirvana or Awakening.
All Buddhist teachings flow from the Four Noble Truths.
The Eight Fold-Path
Right, Integral, Complete, Perfected.
1. Right View, Understanding;
2. Right Attitude, Thought or Emotion;
3. Right Speech;
4. Right Action;5. Right livelihood;6. Right Effort, Energy, and Vitality;7. Right Mindfulness or Awareness;8. Right Samadhi "concentration", one-pointedness. Integration of, or establishment in, various levels of consciousness.