The three basic ideas of Buddhism are the Three Universal Truths.  The first truth says that nothing lasts.  This is called annica.  People, plants, even things like mountains are changing all the time.  The Buddha said that because nothing remains the same for long, there is no rest except Nibbana. 

The second truth is Dukkha.  This mean suffering, but is more than pain.  It means things like being bored and being uncomfortable, as well Dukkha is everything that is unsatisfactory.  For Buddhists, life is Dukkha because there is nothing that is absolutely perfect.  The Buddha said that no-one can escape Dukkha.  His teaching was a way of overcoming it. 

The third universal truth is anatta, which means no soul.  The Buddha taught that there is nothing that can be called a soul.  Instead, he said that people are made up of five parts: feelings, thoughts, awareness, ideas and body.  However, there is nothing in people that carries on into another life, except the force that they make in this life.

These ideas are important because the rest of the Buddha’s teaching is based on them.