Core Chain is a new L1 that combines elements of several other L1s. Understanding what it is and how it works, therefore, will likely be easier after a discussion of other, related blockchain projects.
Bitcoin - In 2009, Satoshi Nakamoto carved digital scarcity from the stone of abundance, for the very first time. Bitcoin’s hard cap of 21 million tokens continues to inspire the token mechanics of blockchain projects almost 15 years later; to this day, it is renowned as the most secure and decentralized cryptocurrency in existence.
Central to Bitcoin’s success are its “miners”, who are tasked with validating new transactions and recording them on the blockchain. This is accomplished through Proof of Work, a demanding procedure that maintains the network's transparency and decentralization by making theft, fraud, and direct attacks outrageously expensive. Though this has proven very resilient, between Bitcoin’s low throughput (a paltry seven transactions per second) and the limits of its underlying programming language, it simply cannot scale enough to support a complex ecosystem of smart contracts.
Ethereum (Pre-Merge) - Before “the merge,”  Ethereum also operated with a PoW consensus mechanism, and was secured by a mining network similar to (but not as decentralized as) Bitcoin’s. Ethereum introduced a rich feature set, including a Turing-complete Ethereum Virtual Machine (EVM) capable of executing smart contracts. This high-level functionality set Ethereum apart, fostering a robust ecosystem of decentralized applications (dApps) and spawning sectors like decentralized finance (DeFi). The tradeoff was that it lost Bitcoin’s level of decentralization and security while still being limited by its PoW mechanism in terms of scalability.
Ethereum (Post-Merge) - Today, Ethereum operates on Proof of Stake. Validators propose and attest to the veracity of blocks on the Ethereum blockchain, and are selected in a pseudo-random way based on the amount of Ether they are willing to 'stake' as collateral. From the early days, Ethereum was designed to transition to Proof of Stake, but the migration has elicited concerns regarding both decentralization and long-term scalability. Over time, concentration of tokens, and therefore network control, is likely particularly as a few custodians and staking pools grow their shares of token management and staking rewards.
Solana - Solana is a high-throughput chain capable of supporting 50k TPS that leverages both Proof of History (PoH) and sharding [Yak]. Solana has very short block times, requiring just 400ms each [Tead], which allows applications built on top of the network to feel like their Web2 counterparts. In order to achieve this level of performance, the requirements for running a validator far exceed those of most other networks [Teae]. This prices smaller players out of the market, limiting the decentralization Solana can achieve. Another tradeoff exists between performance and network availability, which was starkly illustrated with several notable recent chain restarts [McS] [Mil]. Solana also has one of the most active developer communities, but its transition from Solidity to Rust has proven challenging for many.
Polygon - Polygon is a PoS-based L2 scaling solution built on top of Ethereum. Its overall mission is to solve many of the scalability challenges on the main Ethereum chain by leveraging PoS and side chains [Teac]. Polygon has attracted a sizable number of developers because of its EVM compatibility, which allows dApp developers to port their code over with minimal changes [Teab].
BNB Smart Chain - BSC is a hard fork of the Go Ethereum (Geth) codebase. One of the major differentiators between BSC and Ethereum is the latter’s Proof of Staked Authority (PoSA), a consensus mechanism that combines Proof of Authority (PoA) and Delegated Proof of Stake (DPoS) [Teaa]. This new consensus mechanism allows BSC to achieve faster transaction times, higher TPS, and lower fees [CZ]. As with Polygon, many have expressed concern over the centralization of BSC’s validator set. Several factors have given rise to this state of affairs, including the high staking requirements to become a validator, the fact that only two of the twenty-one validators are involved in consensus activities at a time [Tra], and speculation around the tight-knit relationship between the validators and Binance. The claim that Binance itself runs any of the nodes, however, can be disproved with onchain data [BsC].
 The merge refers to Ethereum’s move from PoW to PoS.