In Buddhism what does it mean by the middle way?

The Middle Way can best be understood as the idea of moderation or balance one must have between the need for excessive pleasure and the need for behaviour that is harmful or punishing to oneself. Its exact meaning differs slightly depending on which branch of Buddhism you are focusing on, but to me it describes the idea that any action or behaviour will, when taken to an extreme, be harmful to us, whether that is in having too much or too little of it. In responding to events, we must tailor our actions according to what is right in the specific situation. An example of the necessity of balance can be seen in our relationship with food. Excessive eating is gluttonous, unnecessary and harmful to our health; insufficient nutrition, on the other hand, weakens us and might eventually result in death. We should not abuse ourselves, whether that is by allowing ourselves to have too much of what we want (but do not need) or depriving ourselves of what we need (but may not want, perhaps out of a desire to make ourselves feel pain). The idea that we cannot think of the world in terms of extremes or generalisations is the heart of the Noble Eightfold Path. It describes the view one must have in life in order to achieve liberation.