Short answers, pulled from the story.
Stilicho was a military commander of partly Vandal descent who became the most powerful man in the Western Roman Empire following the death of Emperor Theodosius I in 395. He served as guardian and de facto ruler for the underage Emperor Honorius, repelled multiple barbarian invasions of Italy, and held the western government together until his execution in 408.
Stilicho rose through military service under Theodosius I, who sent him on a diplomatic embassy to the Persian court in 383. After the successful conclusion of peace talks, he married Serena, the emperor's niece. Theodosius promoted him through several commands and, shortly before dying in 395, appointed him supreme commander and guardian of his son Honorius.
On Easter Sunday of 402, Stilicho launched a surprise attack on the Visigothic forces of Alaric at Pollentia, breaking the Gothic siege of Mediolanum and capturing Alaric's camp and his wife. Alaric escaped with most of his men. The battle was the last Roman victory celebrated with a triumphal march in the city of Rome.
Stilicho was arrested and executed on the 22nd of August 408 following a military mutiny at Ticinum on August 13, in which at least seven senior imperial officers were killed. His enemies at court accused him of planning to place his son Eucherius on the imperial throne and of having previously arranged the assassination of Rufinus, a rival in the eastern court.
After Stilicho's execution, the wives and children of barbarian soldiers serving Rome were killed throughout Italy. An estimated 30,000 of those soldiers then joined Alaric, who had twice been repelled from Italy by Stilicho. Without Stilicho to oppose him, Alaric besieged Rome and sacked the city in August 410, the first barbarian capture of Rome in nearly eight centuries.
The main sources are the panegyrics of the court poet Claudian, who was Stilicho's patron and wrote favorably about him, and the historian Zosimus, who covered events after 404 by drawing on two earlier writers: Eunapius, who was hostile to Stilicho, and Olympiodorus, who was supportive. Stilicho also corresponded with the pagan senator Symmachus.