What's the difference between Ethereum & bitcoin?

As a keen observer of the cryptocurrency landscape, I'm often asked to clarify the differences between two of the most prominent players: Ethereum and Bitcoin. Could you please elaborate on the key distinctions between these two? Ethereum, for instance, is often touted for its smart contract capabilities and decentralized applications, while Bitcoin is primarily seen as a digital currency. Could you elaborate on the technical differences, such as consensus mechanisms, scalability, and use cases? Additionally, how do their market positions and community dynamics differ? Understanding these nuances is crucial for investors and enthusiasts alike.