Is Chainlink built on Polkadot?

I'm curious about the relationship between Chainlink and Polkadot. Could you clarify if Chainlink is indeed built on the Polkadot platform? This question is important to me as I'm considering investing in both projects and want to ensure I have a clear understanding of their interconnections. If Chainlink isn't built on Polkadot, could you please explain the nature of their relationship, if any? This would greatly assist me in making informed decisions about my investment portfolio.