How does wBTC bridge work?

Could you please explain how the wBTC bridge operates? I'm trying to wrap my head around the concept. Does it involve a series of complex transactions or is it more straightforward? I'm particularly interested in understanding how it allows Bitcoin to be used on Ethereum-based platforms. Is there a need for a custodian or intermediary in this process? And how does it ensure the security of the bridged assets? I'm eager to learn more about this fascinating aspect of cryptocurrency integration.