In history, animals, people and objects have been reproduced in a three-dimensional way, for different purposes, religious, sexual, to help in hunt, to bring crops, etc. All these representations we can catalog as sculptures.
The earliest reproductions found at prehistorical sites were animals carved in bone or clay. They originate from the same timeframe as sculptures of woman in favour of maternity - Venus of Willendorf or Venus of Lespugue.
Later, we can refer this to different currents in the Greek more hieratic sculptures like those from the temple in Knosos or those of Mesopotamia from the Persian culture. In turn, in Chinese culture sculptures were developed caring their own unique characteristics. Likewise, in four thousand years of Egyptian culture where sculptures are very special and of distinctive cut.
All this leads to an explosion of styles in the sculptures of ancient Greece. Beginning two centuries before the birth of Christ, where it advances in the reality and movement in the sculpture giving it much more realism than in any other cultures, to name Polyphletete Doriphor as na excellent example.
All this sculptural quality was adopted later by the Roman Empire. The Romans initially copied almost all the Greek work and later developed their own styles.
The closer we come to our times the more we see new and different advanced styles being developed in sculpture. We speak of Neorealism, Impressionism, Expressionism, Cubism, Hyperrealism, Constructivist etc.
All these types of sculpture, are advancing in different ways to express each artist, their time and their vision of the three-dimensional. Sometimes, affecting the space, others the air that surrounds each sculpture.
Everything is valid, while what you want to reflect in each of your works, is a new outlook, and a innovative and different concept. So the artist visualises in his artwork his own mind and then uses different materials to express it.