The teachings of the Buddha revolves around this central tenant known as the "Four Noble Truths". The Four Noble Truths form the central foundation of Buddhism. So, what are the Four Noble Truths?
The First Noble Truth states that "Life is Dukka". "Dukka" is very often translated as "sufferings", but I feel it's a very inadequate translation. A much better translation is "Unsatisfactoriness". Basically, the First Noble Truth states that life is unsatisfactory and imperfect. How so? All of us are subject to pain and sufferings. All of us cannot avoid disease, old age and death. We are subject to impermanence and uncertainty. Very often, we have to associate with things that are unpleasant and disassociate with things that are pleasant. All these are unsatisfactory.
The Second Noble Truth explores the source of unsatisfactoriness. Why is it that our lives are unsatisfactory? The answer is within us. Our lives are unsatisfactory because of "Tanha" and "Avija". "Tanha" is very often translated as "Cravings", but a much better translation should be "Thirst". "Avija" means "Ignorance".
What is "thirst"? Thirst is our natural tendency to clinging on to the pleasant and be aversed to the unpleasant. Most of us spend most of our lives chasing after and clinging on to things that satisfy our desires, egos, lusts, etc, and trying to run away from things we find painful, unpleasant etc. All these come under the umbrella of "Thirst".
What is "Ignorance"? Not to know that all conditioned things are impermanent is "ignorance". Not to know that all conditioned things are unsatisfactory is "ignorance". Not to know that all things are "without essence of self" is "ignorance". And not to know the Four Noble Truths is "ignorance". (The "ignorance" part is a little profound, I admit).
Is there a way to overcome "thirst" and "ignorance" then? That's the question the 3rd Noble Truth answers. The 3rd Noble Truth says, yes, there is a way. There is a way to overcome "thirst" and "ignorance". When that is done, one becomes calm and blissful. There is no more sufferings. There is no more unsatisfactoriness in life. That state of being is called "Nirvana".
Cool. But how do you overcome "thirst" and "ignorance" then? That's where the 4th Noble Truth comes in. The 4th Noble Truth is a package of self-cultivation that enables the practitioner to attain the goal of "Nirvana".
There are 8 parts in this package of self-cultivation. That's why it's also called the "Eight-fold Path". The 8 parts are: Perfect Thougths, Perfect Actions, Perfect Speech, Perfect Livelihood, Perfect Effort, Perfect Mindfulness, Perfect Concentration, and Perfect Understanding.
The 8-fold path can be grouped into 3 groups. The first is "Morality". The idea here is to live a life where one tries to constantly practice kindness and love, and to live life such that one's conscience is clear. That comes from our practice of Perfect Thougths, Perfect Actions, Perfect Speech and Perfect Livelihood. Basically, we live life to the best that we can.
The 2nd group is "Concentration". With a clear conscience cultivated with "morality", we cultivate our minds so that it'll be calm, peaceful and concentrated. This comes from our practice of Perfect Effort and Perfect Concentration.
The 3rd group is "Insight". With a very strong, calm, concentrated and peaceful mind, we learn to work with ourselves, to gain insight into ourselves, to eventually overcome all our problems and all the unsatisfactoriness in our lives. This comes from our practice of Perfect Mindfulness and Perfect Understanding.
In a nutshell, the above is Buddhism. Basically, we see the Buddha as a doctor here to solve a problem: unsatisfactoriness. In ancient Indian culture, the doctor performs 4 steps: he identifies and acknowledges the problem, finds the source of the problem, state that there is a cure, and prescribes the cure. The 4 Noble Truths can be seen as such an exercise. The 1st Noble Truth acknowledges that the problem of Dukka exists. The 2nd finds the source. The 3rd states that a solution is possible. And the 4th prescribes the solution.