Ethereum is a blockchain based, open sourced, software platform that focuses on allowing developers to create and launch decentralized applications, also known as DAPPS.

Ethereum is second on the list at coinmarketcap.com.

The current price of each Ether is $50
The circulating supply of ether tokens is 91 million
The market cap for ether is 4.5 billion
The 24 hour volume is around 52.9 million.

If you’re new to reading these price charts, let me explain what these numbers mean.
The price listed is how much it costs to purchase one coin.
The circulating supply is the number of coins that exist at this moment.
The 24 hour volume is the amount of money being exchanged in the act of buying and selling the coin in the past 24 hours.
And the market cap is roughly the total value of all coins in circulation. Or in other words, it’s the price multiplied by the circulating supply.

Vitalik Buterin

is the co-founder of Ethereum, he’s a Russian Programmer and also a co-founder of Bitcoin magazine.
He’s also 23 years old, but when you learn that his favorite toy growing up was playing with Microsoft Excel, things start to make sense. He was attending the University of Waterloo but dropped out when he was granted the Thiel Fellowship by the famous entrepreneur Peter Thiel (the man behind Paypal)
Vitalik then went on to work with Bitcoin full-time, before eventually co-founding Ethereum.

Bitcoin revolutionized how we think about and transfer money, and I believe that Ethereum will revolutionize how we think about and conduct business.
This is accomplished by things called smart contracts.

Smart contracts refers to computer code that facilitates the exchange of money, content, property, shares, or anything of value.

When run on the blockchain a smart contract becomes like a self-operating computer program that automatically executes when specific conditions are met. Because smart contracts run on the blockchain, they run exactly as programmed without any possibility of censorship, downtime, fraud or third party interference.

Unlike most other blockchains that are limited to being only peer-to-peer digital currencies, the Ethereum blockchain allows for anyone to run almost any program regardless of the programming language. This is possible thanks to what is called the Ethereum Virtual Machine.

The Ethereum Virtual Machine makes the process of creating blockchain applications much easier and efficient than ever before. Instead of having to build an entirely original blockchain for each new application, Ethereum enables the development of potentially thousands of different applications all on one platform.

The beauty of Ethereum is that in addition to being an open sourced blockchain that facilitates dapp development by all, Ethereum also intuitively incorporates it’s token, ether, into the blockchain. Ether is more than just a crypto coin, it is a necessary component in any transaction or smart contract on the ethereum blockchain. This gives ether a very real purpose.

Just like how a car needs gasoline to be in motion, smart contracts on the ethereum blockchain need what is called “gas” to complete the process. The only currency accepted to pay for this “gas” is ether.
https://www.cryptocompare.com/coins/guides/what-is-the-gas-in-ethereum/

If you’re interested in learning more about what it takes to develop a decentralized app or DAPP with Ethereum, check this out

Additional Reading and Sources:

Blockgeeks Article- What is Ethereum
CoinDesk Article on Ethereum's World Computer
CoinDesk Article on Ethereum Update: Metropolis
CoinMarketCap
Beginner's Guide to Ethereum's Smart Contracts
Designing Dapps on Ethereum