To answer your question on what a blockchain looks like, please check out this interactive site!
In the case that you send an incorrect amount of bitcoin in a transaction, you can remedy this by having the receiver return whatever excess coin you sent. Otherwise, since the Bitcoin blockchain is immutable, you will not be able to modify the amount of coin sent in a transaction.
There are also many benefits outside of the financial sector of this technology. There are applications in supply chain fraud, voting, delivery of energy sources, and smart contracts to name just a few. I’d suggest reading more on these topics.