People seem to be using 'Ethereum' and 'Ether' interchangeably when in reality they are different things.
Ethereum is platform/network and Ether is fuel that powers the network. You can compare it with Car and fuel.
Ether is how you pay on Ethereum network, for example, you need Ether to pay fees on Ethereum.
Ether can be bought and sold, and its price also fluctuates based on the supply and demand. So, when somebody says that he has invested in Ethereum, he has actually bought Ether.
