Bitcoin (BTC) and Ethereum (ETH) are both cryptocurrencies, but they serve different purposes. Bitcoin was created as a digital currency and is often referred to as "digital gold." It primarily functions as a store of value and a medium of exchange. Ethereum, on the other hand, is a blockchain platform that enables the creation of decentralized applications (DApps) and smart contracts. While both have their own blockchains, Ethereum's blockchain is more versatile and programmable, allowing developers to build a wide range of applications beyond simple transactions.

Both Bitcoin and Ethereum use a process called "mining" to validate transactions and add new blocks to their respective blockchains. Bitcoin mining involves solving complex mathematical puzzles through specialized hardware known as ASICs (Application-Specific Integrated Circuits). Ethereum mining also uses a similar proof-of-work (PoW) mechanism but is transitioning to a proof-of-stake (PoS) system called Ethereum 2.0, which will rely on validators instead of miners to secure the network.

Bitcoin has a capped supply of 21 million coins. This limited supply contributes to its perception as digital gold and is designed to control inflation. Ethereum's total supply is not capped, but it has an annual issuance limit to control inflation. The switch to Ethereum 2.0 aims to reduce the issuance further by transitioning to PoS and potentially introducing a deflationary mechanism.

Bitcoin is primarily used as a digital store of value and a means of transferring value across borders. It's often compared to gold due to its scarcity and store-of-value characteristics. Ethereum, in addition to being used as a digital asset (Ether), powers a wide range of decentralized applications (DApps) and smart contracts. It's a platform for developers to build decentralized solutions for various industries, including finance, supply chain, and gaming.

Bitcoin is generally considered secure due to its long history and robust network. However, scalability remains a challenge, as high transaction volumes can lead to slower confirmations and higher fees during network congestion. Ethereum faces similar scalability challenges, which is one reason it's transitioning to Ethereum 2.0 with a PoS consensus mechanism to improve speed and reduce energy consumption. Security in Ethereum also relies on the proper execution of smart contracts, which can be vulnerable to bugs and exploits.