Ethereum is a smart contract platform that allows users to program applications that run on the blockchain. Learn more about Ethereum here: https://www.defilava.com/post/what-is-ethereum-and-why-should-you-care
Between September 13th and 15th of 2022, the Ethereum merge successfully went live after several failed attempts to move to Proof of Stake.
The Ethereum Merge in brief:
The current Ethereum Mainnet merges with the Beacon Chain proof-of-stake system.
This marks the end of proof-of-work for Ethereum, and the full transition to proof-of-stake.
This sets the stage for future scaling upgrades, including sharding.
The Merge reduces Ethereum's energy consumption by ~99.95%.
As Mainnet merges with the Beacon Chain, it merges the entire transactional history of Ethereum.
Instead of using miners (Proof of Work) to secure the network, Ethereum will now use validators which are created by staking Eth tokens on the network. With mining, computer nodes compete to solve a cryptographic puzzle in order to confirm the next block and obtain the network rewards. With Proof of Stake, validators are selected by a pseudo-random selection algorithm based on the staked deposit. This is how less energy is used, since the algorithm selects the validator as opposed to all the miners competing against each other.
While there are many issues to discuss in the Proof of Work vs Proof of Stake debate, the main wildcard when it comes to the Ethereum Merge is regulation. With the move to Proof of Stake, Ethereum becomes even more of an "unregistered security" than it already was.
Securities are fungible and tradable financial instruments used to raise capital in public and private markets. There are primarily three types of securities: equity—which provides ownership rights to holders; debt—essentially loans repaid with periodic payments; and hybrids—which combine aspects of debt and equity.
Ethereum certainly fits this description, unlike Bitcoin, which has been declared a commodity by Gary Gensler of the SEC. While the SEC has avoided giving a straightforward verdict on Ethereum, it is pretty clear by the rhetoric that Gensler views most other tokens besides Bitcoin as securities.
For more on the Ethereum merge, reference these sources: