Short answers, pulled from the story.
Sergius of Radonezh was born between 1314 and 1322 in the village of Varnitsa near Rostov Veliky. His parents Kiril and Maria belonged to a boyar family that had fallen into poverty after Ivan I of Moscow seized their home region.
Bartholomew took monastic vows and received the name Sergius before spending over a year alone as a hermit. He later built a small monastic cell and a church dedicated to the Trinity with his brother Stefan on Makovets Hill.
Disciples of Sergius founded approximately forty monasteries that extended his influence geographically across central and northern Russia. These communities included Borisoglebsky, Ferapontov, Kirillo-Belozersky, Vysotsky, Andronikov, and Simonov monasteries.
Sergius died on the 25th of September 1392 after decades of ascetic practice. His incorrupt relics were discovered thirty years later in 1422 and placed in the new cathedral of Troitse-Sergiyeva Lavra which he originally founded.
The Catholic Church officially recognized Sergius in modern times and added him to the liturgical calendar authorized for Russian Catholics in 1940. Several churches within the Anglican Communion honor him in their Calendar of Saints with a specific commemoration on the 25th of September.