Short answers, pulled from the story.
Stoicism is a philosophical movement and practical guide to living that emphasizes daily self-discipline and moral improvement. It was founded by Zeno of Citium in the ancient Agora of Athens around 300 BCE, and it taught that the universe operates according to reason, or logos.
The name Stoicism derives from the Stoa Poikile, or painted porch, a colonnade on the north side of the Agora in Athens decorated with mythic and historical battle scenes. Zeno of Citium and his followers gathered there to discuss their ideas, and the school was originally known as Zenonism before that name was dropped.
Stoic philosophy is traditionally divided into three interconnected disciplines: logic, physics, and ethics. Stoic logic examines reason through propositions and arguments, physics treats the Universe as a material reasoning substance, and ethics centers on virtue as the highest good and the path to eudaimonia.
Chrysippus of Soli, who lived from about 279 to about 206 BCE, was the third head of the Stoic school and the outstanding figure in Stoic logic. He built a system of propositional logic, introduced the main logical connectives, and listed five basic argument forms called indemonstrables to which all other arguments reduce.
The Stoics taught that virtue is the only good and is sufficient for happiness, while external things like health, wealth, and pleasure are indifferent. They held that destructive passions such as anger, fear, and grief result from errors of judgment, and the wise person, or sophos, achieves apatheia, freedom from these passions.
Stoicism was the original philosophical inspiration for modern cognitive psychotherapy, mediated by Albert Ellis' rational emotive behavior therapy, the major precursor of cognitive behavioral therapy. The depression treatment manual by Aaron T. Beck traces cognitive therapy's origins to the Stoic philosophers, echoing Epictetus' teaching that it is our judgments about events, not the events themselves, that upset us.
Stoic logic declined after Christianity became the state religion in the 4th century CE, and the Neoplatonists adopted Aristotle's logic instead, so the Stoic writings did not survive intact. Stoic logic as a system was lost until the 20th century, when logicians such as Jan Lukasiewicz and Benson Mates reappraised it using the modern propositional calculus.