Short answers, pulled from the story.
Gopala founded the Pala Empire after being selected by feudal chieftains in Gauda to restore order following civil war. His ancestry remains unclear, though some sources suggest he came from a family of menials or Dasajivinah while others claim legendary origins involving a tree-god.
Dharmapala expanded the empire significantly during the early ninth century after defeating Indrayudha of Kannauj and installing his nominee Chakrayudha on the throne. This expansion brought several smaller states in North India under his suzerainty as far as Jalandhara before Nagabhata II checked his power.
The capital of the Pala Empire was Gauda, which Mahipala I recovered within three years of ascending the throne in 978 CE. The empire stretched across the Gangetic plain from Bengal to parts of northeastern India and Nepal with territory fluctuating due to constant hostility from rival powers.
The Palas were patrons of Mahayana Buddhism because rulers like Dharmapala established major monasteries such as Vikramashila and Somapura Mahavihara. These institutions attracted students from across Asia including Tibet and Southeast Asia while developing centers of learning that reached their height under Pala patronage.
The Pala Empire maintained the largest elephant force among contemporary powers despite lacking good native horse breeds for cavalry. Arab merchant Sulaiman claimed the king would lead fifty thousand war elephants during battles while Ibn Khaldun mentioned five thousand suggesting exaggeration in some reports.