This commentary was completed late in his life (1040 - 1105), and may be a compilation of the lectures he offered at the yeshiva (college) he founded in Troyes. There is a recent phrase in social media: ELI5, which means "Explain Like I'm 5," asking the teacher to put something into very simple terms for easy understanding. Rashi's commentary has been described as so simple that a five-year-old could understand what he is saying.
His focus seemed to be on grammar and syntax, and he defined unusual Hebrew words to explain why that word was chosen over another and the nuances of word choice. He was careful to distinguish between the plain meaning of a word and the rabbinic interpretation of it.
Rashi also wrote the first (near-)comprehensive commentary on the Talmud (the primary source of Jewish law). Phrase by phrase, he went through 30 of the 39 tractates (organizational elements), explaining the meaning of the words and their result. To make things more comprehensive, he often used analogies to common knowledge of daily life, professions, or crafts. He also translated difficult Hebrew or Aramaic words into the local language, Norman French. This attention to vocabulary has given modern scholars insight into spoken French of the 11th century.
His commentaries became "instant classics." They were copied and spread far and wide and embraced by both Ashkenazi and Sephardic Jews.
Near the end of his life he experienced the mass murders of Jews caused by the followers of the People's Crusade (the unofficial first phase of the First Crusade) as they traveled through Europe, fired up with pro-Christian sentiment and the fervor to free the Holy land from non-Christians. Rashi wrote several poems mourning the destruction. Three sons of his teacher, Isaac ben Eliezer Halevi, were killed during this time.
Rashi died at the age of 65 and was buried in Troyes. Although the location of his grave was noted, that information was lost over time. The Jewish cemetery land is now a public square in Troyes, and a monument to Rashi was erected by French Jews. There is a legend, however, that because of the prominence of his life and works—impossible to produce by an ordinary man in one lifetime—that he was so clearly inspired by the Shekinah, the Holy Spirit, that he did not die a natural death. Instead, he was assumed bodily into heaven like the prophet Elijah.
The fifth paragraph mentions that his commentaries were accepted by both Ashkenazi and Sephardic Jews. What was the difference, and why did it exist? I'll explain that tomorrow.