Ethereum is a decentralized platform that runs smart contracts: applications that run exactly as programmed without any possibility of fraud or third party interference. Ethereum is used to build decentralized applications (dapps) on its platform.
Ether, the native cryptocurrency of Ethereum, is mined through a Proof of Work (PoW) consensus algorithm (like Bitcoin). Miners are rewarded for validating blocks with Ether. Ethereum miners are rewarded based on their share of work done, rather than their share of the total number of blocks mined.
The amount of time it takes to mine one ethereum block varies depending on the mining difficulty and the price of ether. Currently, miners are rewarded with three ether for each block they mine.
However, this amount will eventually decrease to two ether per block as more ether is mined and deployed on the ethereum network. The ethereum network is still in its early stages, and the mining difficulty and rewards will continue to change over time.