Satoshi Nakamoto is the name used by the person or people that created Bitcoin and wrote the Bitcoin white paper. 

The name first appeared on the paper “Bitcoin: A Peer-to-Peer Electronic Cash” that was distributed by a cryptography mailing list in 2008. The very first Bitcoin transaction took place between Satoshi and Hal Finney, a cypherpunk and programmer. While some suspect that Hal Finney may be the person behind the Satoshi pseudonym, it was never proven. After a five-year battle with ALS, Hal Finney passed away in 2014.

In 2010 Satoshi handed over control of bitcoin to the community members and stopped working on it himself. Up to that point, all of Bitcoin’s code had been written by him and him alone. Bitcoin’s goal is to act as a payment processor with its own cryptocurrency. Bitcoin’s evolution has shown to be a reliable way to send money anywhere in the world, all while avoiding the high fees and long settlement times associated with transferring currency across borders.

Ethereum is able to compute anything computable given enough resources and is therefore Turing-complete. In simpler terms, it can simulate a computer. Bitcoin’s main focus is payments and is not Turing complete. It only provides a very simple mechanism to distribute money. This reflects Ethereum’s main goal, to become the so-called “World Computer”, allowing rules to be written in any way that can be expressed by code and enable smart contracts.

While Bitcoin has transaction fees, Ethereum uses a pricing mechanism known as gas. Each smart contract or transaction requires a set amount of gas, which must be purchased with ether at the time of the transaction. The price of gas varies based off of network activity and congestion.

Eth Gas

Gas is not a token or coin. Gas is a pricing mechanism used to determine how much Ethereum should be required to purchase computing power on the Ethereum Virtual Machine. When someone pays for a transaction or smart contract execution, the gas price is determined based on current network volume. The user then pays for gas with their Ethereum in order to execute the transaction or smart contract computation.

It may help to think of gas as a computing credit, which can be purchased initially to fund a smart contract, but which changes in value over time depending on network availability.