What network is Celo on?

As a professional in the realm of cryptocurrency and finance, I'm curious to know more about the underlying technology behind various projects. Specifically, with regards to Celo, I'm interested in understanding what network it is built upon. Is it a fork of an existing blockchain? Or is it a novel design? The network architecture is crucial for understanding its scalability, security, and interoperability. Additionally, knowing the network allows for a deeper analysis of its potential impact on the broader cryptocurrency landscape. Therefore, could you please elaborate on what network Celo is currently utilizing?