The Buddha was a man born approximately 2500 years ago in ancient India. He set the wheel of truth turning through his realizations and teachings of The Four Noble Truths.
Gautama Buddha broke through the cultural norms of his times and realized a truth that still applies to this day. It is said that it took six years for Buddha to fully awaken. A part of awakening is overcoming your inner demons. This is what Buddha accomplished too.
What this means is that Buddha worked hard at becoming enlightened, or awakened to truth. It did not come easy. It was not revealed to him by a mystical means. He learned from various teachers of his day. He tried asceticism which was a form of neglect. He also realized that extremes of wealth did not bring contentedness either.
He awakened through an experiential process. In this manner the Buddha realized The Middle Way is a good way to find inner and outer peace in a confusing world. That too much, or too little of anything is probably not that good. That somewhere in-between there is the right amount. The right amount of anything that life requires in order to see true reality and thus be awakened.
The Buddha explains this to Sona, one of his followers with the story of how to best tune a stringed instrument such that it produces a fine sound. Strings too loose, not good. Strings too tight, not good. Strings tuned in the middle, just right.

The Tathagata

He is now known as Buddha, but the word Buddha refers to anyone who has awakened in what could be called a real sense that constitutes a true spiritual sense. The word Buddha does not exist in the Pali Canon and The Buddha never referred to himself as Buddha.
He referred to himself as the Tathagata, meaning 'thus gone' or 'thus come'. Tathagata basically refers to the fact that the man, Siddhatta Gotama, had awakened. That he realized the truth of existence and realized full enlightenment through the shedding of false beliefs and having no illusions obscuring his senses.

Three Characteristics

The Buddha said there are three characteristics that are important in understanding life and ulitmately awakening. These are the truths of impermanance, suffering, and not-self, sometimes people will say no-self. Also, people will argue over the difference. If there is one!
Impermanance is obvious, in that all things, absolutely everything, including you and everyone you know and don't know will arise and pass away. This refers to all things in existence being subject to this same truth no matter what these things are.
Suffering is the next characteristic. I prefer unease, dis-ease, or any number of words that scholars are now using instead of suffering. Anyway, if you look close enough you will see that a certain unease, sometimes powerful, sometimes near imperceptible, pervades all life. This unease can and does exist even during joyous times. This characteristic exists as anxiety, panic, depression, fear, etc.
Not-Self is the third characteristic that the Buddha realized and taught about. Many people think this means that we don't really exist, that we are illusions or something of that matter. The truth is we do exist and we do have a self. I believe what the Buddha was referring to is that the self, that inner essence, is often layered with misconceptions of who and what we are. That, we are not what we think we are in most cases.
Are we our thoughts? In essence, we have so much going on in our minds that we believe we are, to a lesser or greater extent, these thoughts that are constantly pervading our minds. In truth we are what is there without the thoughts. This is what meditation helps us to attain.
The Buddha was also referring to the fact that even our mind is constantly in a state of change or flux. That it too, is not permanent.
Further, this third characteristic of not-self is not that you are not a self, or that you don't really have a 'self', but that your 'self' is composed of, and clouded with perceptions that you generate. Once you start the path of learning truth and wisdom this perception begins to fall away and you are 'not' what you 'thought' your 'self' to be.
The Buddha spoke a language or dialect that is unknown. He did not speak Pali, nor did he teach in Sanskrit. It is said that he always chose to teach in the language of those he was teaching to. In this way there would be no mis-translations of what he taught.
His teachings were carried forward orally. That is, the telling and re-telling of his teachings are what survived. Nothing was written down until a few hundred years after his death. There are people that try to justify this as a good thing? I, for one, would have preferred that Buddha wrote what he taught down. Then there would have been less doubt as to what he actually taught.
Anyway, the languages that were spoken during this process would have had a major impact on the intention of the teachings. Also, these languages had to be translated into English (and other languages) so we can understand. This too would have an affect on our understanding of what the Buddha intended.
I believe what Sakyamuni Buddha taught is that when our minds are grasping and clinging to the various aspects of life we never seem to be content, or satisfied. If we are, then it's short-lived. We cling so as to find happiness. But the unbinding process does not occur when we function in this manner.
There is much debate over these characteristics and other aspects of Buddhism. I believe many people have made it more difficult then it has to be. This happens because of some clear and distinct reasons -more reason as to why clarity of mind helps us to understand.
The Buddha is continued with the link below.

The Buddha Part 2 .END=OM MANI PADME HUM.( 3 TIMES ).RESEARCH TIBET DHARMA BY VENERABLE GESHE TESERING TASHI.VIETNAMESE TIBET NUN.28/1/2012.NEW ZEALAND.