Ethereum vs. bitcoin: What’s the difference?

Bitcoin and Ethereum are both cryptocurrencies, but they're quite different
With bitcoin having entered this world as the very first global cryptocurrency in 2009 and Ethereum only showing up in 2015 as a potential alternative.
The most successful cryptocurrency for storing value continues to be bitcoin. As the most valuable coin in the world by quite some margin — and the progenitor of the entire cryptocurrency revolution — bitcoin has proven itself. It’s far more recognized than any of its peers, and that makes it easier to buy, store, and sell.

Bitcoin’s sole purpose is to be the virtual currency of the internet, and uses blockchain to do this.

Ethereum focusses on the bigger problem.
Here’s a little bit about Ethereum:

Ethereum was created in 2015 by a man called Vitalik Buterin. Vitalik had the vision of not only having a decentralised cryptocurrency (like Bitcoin) but also allowing decentralised applications to be created on the Ethereum blockchain that use Smart Contracts.
Although bitcoin is better at storing value than Ethereum, at least for now, Ether has quickly become a preferred method for transferring wealth to and from people and entities. In the middle of 2017, it overtook bitcoin in the number of daily transactions, and that shows no sign of stopping, with more than double the number of transactions taking place with Ether on a daily basis at the time of writing.
This is because Ethereum can be used as a platform for other cryptocurrencies, and also because Ether transactions tend to be confirmed quicker by the blockchain. It’s built to be more efficient than bitcoin, partly through virtue of being a newer and more optimized cryptocurrency.

Cryptocurrencies are nothing if not volatile, though, and as much as it seems most likely that bitcoin will remain the king of the cryptocurrencies for the foreseeable future, there is no guarantee of that.