Casper was a series of upgrades aimed at improving Ethereum’s scalability, security, efficiency, and reducing its environmental impact. It was a crucial step in Ethereum’s move toward what was once called Ethereum 2.0 — now simply known as Ethereum after the implementation of The Merge.

Casper came in two main versions:

1. Casper FFG (Friendly Finality Gadget)

The first transition phase between PoW and PoS. It enabled a hybrid approach where blocks were still created by PoW, but validated through PoS rules.

2. Casper CBC (Correct-by-Construction)

A more theoretical version developed by Vlad Zamfir, focusing on designing a secure and flexible PoS consensus system.

The transition from Ethereum 1.0 to 2.0 is dubbed the “Serenity” upgrade. It will consist of three different phases. 

- In its initial phase (Phase 0), a new blockchain called Beacon Chain will be launched. Casper FFG rules will drive the consensus mechanism of this new PoS-based blockchain.

- Unlike PoW mining, where miners run expensive and specialized machines to create and validate blocks of transactions, Casper implementation will remove the process of mining from Ethereum.

-  Alternatively, the verification and validation of new blocks of transactions will be done by block validators, which will be selected according to their stake.

- In other words, the voting power of each validator will be determined by the amount of ETH they put at stake.

-  For example, someone who has deposited 64 ETH will have double the voting weight of someone who deposited the minimum staking amount.

- To become a block validator in the first phase of Serenity, users will need a minimum stake of 32 ether (ETH) - deposited into a special smart contract based on the former Ethereum blockchain (1.0). 

- Random committees of validators will be selected to propose new blocks and eventually receive block rewards for doing so. The block rewards will likely consist only of transaction fees as there won’t be a block subsidy. 

It is worth noting, however, that each PoS implementation may present a different approach, with different rewarding models. 

1. Reduced Environmental Impact

- Proof of Stake (PoS) systems don't require as much effort to validate transactions, meaning miners don't need high-powered hardware or spend as much on electricity.

- This means lower costs and less environmental impact — something that's especially important now that Bitcoin mining consumes more energy than many countries.

2. Increased Scalability

- Proof-of-Work requires every transaction to be validated by every node in the network before it can be completed.

- It uses a different validation method which would allow Casper to process more transactions per second, leading to faster and cheaper transactions overall.

3. Energy Efficiency

- The big benefit of moving to proof-of-stake is that it will be more energy-efficient. In the long run, this will allow the amount of Ether in circulation to grow at a controlled and sustainable rate.

4. Casper protocol’s ultimate objective is transforming Ethereum to its version 2.0, which is also given the name of “Serenity.” Ethereum 2.0 aims to be faster, more efficient, and highly scalable.