"Emptiness" is a concept that appears in Buddhist philosophy, especially in the Mahayana (incl. Zen) and in the Vajrayana (Tibetan) traditions. Emptiness is the most common translation of the term "sunyata", and has also been translated as "void" or "voidness". The term is most often confused, sometimes on purpose by critics, to mean emptiness =nothingness. This misconception has then led to the notion that Buddhism is nihilistic, and that it teaches that nothing exists. This is far from the true viewpoint Buddhism expounds, as Buddhism shuns all extreme views such as this. The Buddha himself said it is better to view all things as real and permanent than to think nothing exists. You'd be technically wrong, but you'd avoid being like those Germans in The Big Lebowski.

To get the true meaning of the word, you should try and see what things are said to be empty of. They are said to be empty of inherent, isolated and permanent existence. That is, all phenomenon, including us people, only exist as a sum total of all other phenomenon in the universe and as a result of their causal relationship with phenomena that preceded them. All things are linked, and cannot be said to ultimately exist by themselves.

As a popular example shows, a car only exist because of it's constituent parts: the engine, wheels etc. It also exists because of the processes that caused it to come into being, such as the factory, the workers and the designers etc. It also exists because of the actions and observation of it by sentient beings, ie., us.

You can see how a car has no Platonic essence of "carness" to it that somehow magically attaches itself to it once it's ready to roll off the production line. It is solely the sum of the parts and the causal conditions that led to its existence.

It is therefore, in Buddhist terminology, Empty - Empty of "carness".

But, as you'd find out if it ran you over, it's certainly real, just not as we habitually take it to be. Breaking this habit of seeing things wrongly is therefore goal.

The sum of this interrelated totality of all things is the Great Void - it is not a yawning abyss, but rather the source and sum of all things. As no object or other form of causally conditioned phenomenon can exist separately from it, all objects are part of it and are a manifestation of Emptiness.

This subject is the central point of many Sutras and Shastras, most notably the Prajna Paramita Hridaya Sutra, also known as the Heart Sutra.