It can at times be difficult to find something that approaches the "simple truth" so here it is.
Buddha taught 3 characteristics, marks, or seals of existence. Annica, Anatta, and Dukkha (in romanized Pali):
Nothing is permanent, unchanging or absolute. Thus, we have no permanent, unchanging, or absolute identity or self. Without a fixed or stable identity, we experience disappointment and dissatisfaction. He called it a cycle of death and rebirth, Samsara.
He also taught that a careful and accurate analysis and application thereof based on these characteristics can also lead to liberation from this cycle. He said that the correct understanding of this can lead to liberation, or Nirvana.
He also said that understanding what it was that he was saying can bring liberation in a certain period of time, then he said no, yet a shorter length of time, then no, even shorter (see Satipatanna Sutta). The implication is clear. And this statement is found in the Pali canon, which many consider to be the bedrock of Buddhist teaching.
(The illustration is a symbol for the Triratna, The Triple Gem, The Three Refuges, the Buddha, the Dharma, and the Sangha)