Short answers, pulled from the story.
The Parthian Empire was founded in 247 BC by the chieftain Arsaces I, who led the Parni tribe into the province of Parthia. This event marked the end of Seleucid control and the start of the Arsacid dynasty that would rule for nearly five centuries.
The Parthian Empire ended on the 28th of April 224 AD when Ardashir I killed the last ruler Artabanus IV at the Battle of Hormozdgān. Ardashir I then established the Sasanian Empire, which assumed the legacy of the Parthian state and ruled until the Muslim conquests of the 7th century AD.
The Battle of Carrhae resulted in a catastrophic defeat for the Roman general Marcus Licinius Crassus and his seven legions against the Parthian forces led by Surena. Approximately 20,000 Roman soldiers died, 10,000 were captured, and Crassus himself was killed during a parley with the Parthian commander.
The Parthian Empire served as a vital hub on the Silk Road by taxing the Eurasian caravan trade in silk, pearls, spices, and exotic animals. Parthian merchants, particularly the Sogdians, acted as middlemen who transported luxury goods between the Roman Empire and the Han dynasty of China.
The Parthian Empire was plagued by civil wars because the nobility, specifically the House of Suren and the House of Karen, held great power over the succession and deposition of Arsacid kings. The decentralized government structure with semi-autonomous kingdoms further weakened central authority and encouraged internal strife.