Does Arbitrum run on Ethereum?

Excuse me, could you please clarify for me if Arbitrum operates specifically on the Ethereum blockchain? I'm trying to understand if it's a sidechain, a layer 2 solution, or if it has an independent infrastructure, but still somehow interacts with the Ethereum network. It would be immensely helpful if you could elaborate on the technical details behind its integration with Ethereum, if any. Thank you in advance for your insight.