The flow of Ethereum consensus as per the answer in this question Smart contracts code: what are nodes in Ethereum actually agreeing upon during the consensus process?
explains somewhat similar consensus to bitcoin. However, bitcoin reaches the creation of block in 10 min and how is this possible for 20 sec in Ethereum??
Bitcoin block creation is much slower than it needs to be. Satoshi guessed that it might take a minute or so to get blocks across the network, meaning that with a 10 minute block time about 10% of blocks would be orphaned, which she probably picked because it sounded reasonable. In practice propagation is normally done in a few seconds. Other coins like LiteCoin that are otherwise near-copies of Bitcoin tweaked that parameter to be lower and they still work fine.
The key trade-off is that faster blocks cause higher orphan rates, and high orphan rates are thought to promote miner centralization. Ethereum uses a system called GHOST to reward miners whose blocks get orphaned which reduces this effect, allowing faster blocks than would be safe otherwise. But it's not a 30x effect: The main difference is that the Ethereum designers had data from actual usage of Bitcoin and other coins, so they were able to choose less conservative settings than Satoshi had.
