Stoicism was one of the most important schools of philosophy of the Hellenistic and Roman world. Many educated people claimed to be stoics, and some scholars also argue Christianity borrowed some of its own ideas from Stoicism.
The founder of Stoicism was a man named, Zeno who lived from the dates 336-264 B.C. As one could imagine, he was heavily influenced by the great Socrates through the works of Plato. After Zeno, his followers made Stoicism into a full worldview with its own logic, epistemology and cosmology.
We can summarize Stoicism with two main points.
First, Stoicism emphasized the importance of self-control and fortitude. Stoics believed that this was important, because if a person was able to overcome irrational emotions, then a person can understand the universal reason (logos). In this way, Stoics believed that a person could live in accordance with nature.
Second, Stoicism had a very deterministic view of the world. In view of this they learned to accept things as they were. In other words, if they could not change the world, then they could at least change their wills. Through discipline they sought to do this.