Short answers, pulled from the story.
Ivan the Terrible, born Ivan IV Vasilyevich on the 25th of August 1530, was the first Tsar of all Russia, ruling from 1547 until his death in 1584. Before that he served as Grand Prince of Moscow from 1533, when he succeeded his father at age three.
The Russian epithet grozny, translated as "terrible" in English, carried an older meaning closer to "formidable" or "awe-inspiring" in Russian. Vladimir Dal defined it in archaic usage as "courageous, magnificent, magisterial and keeping enemies in fear, but people in obedience." The modern English connotations of defective or evil are not part of the original meaning.
The oprichnina was a separate territory within Russia, primarily carved from the former Novgorod Republic, that Ivan established in 1565 after staging a dramatic abdication and demanding absolute power as his price for returning. Ivan ruled the oprichnina personally through a paramilitary guard called the oprichniki, originally numbering 1,000 men, who were exempt from normal legal accountability and used to persecute the boyar nobility. Ivan formally abolished the system in 1572 after the oprichniki performed poorly against Crimean Tatar forces.
Historians generally believe that on the 19th of November 1581, Ivan fatally struck his son Ivan Ivanovich in the head with his pointed staff during an altercation. The incident, which also caused a miscarriage for Ivan Ivanovich's wife Yelena Sheremeteva, is the subject of Ilya Repin's celebrated 1885 painting. This left Ivan's younger son Feodor to inherit the throne; Feodor died childless in 1598, ending the Rurik dynasty.
Ivan launched the Livonian War in 1558 to secure access to the Baltic Sea and its trade routes. The 24-year conflict drew in Sweden, Poland-Lithuania, the Teutonic Knights, and eventually the Ottoman Empire. Russia lost. The war ended in 1582 with the Truce of Yam-Zapolsky and in 1583 with the Truce of Plussa, stripping Muscovy of its presence in Livonia and its access to the Baltic entirely.
Stalin decided Soviet historians should praise strong leaders who expanded Russia and directed both Alexei Tolstoy and Sergei Eisenstein to produce works celebrating Ivan. After reading their scripts together following the Battle of Kursk in 1943, Stalin praised Eisenstein's first film but rejected Tolstoy's play. When Eisenstein's second film portrayed Ivan suffering pangs of conscience, Stalin suppressed it; it was not released until 1958.