I started with Ted Talks to give me a basic understanding about blockchain technology then went from there. I'd also recommend reading the Bitcoin whitepaper. Bitcoin is the OG blockchain and it's whitepaper explains how it works, and why it's such a revolutionary technology.
https://bitcoin.org/bitcoin.pdf
If you want to dig further into the technology I'd recommend reading this book:
https://www.amazon.com/Business-Blockchain-Practice-Application-Technology/dp/1119300312/ref=tmm_hrd_swatch_0?_encoding=UTF8&qid=&sr=
It's a really good read if you're really interested in blockchain. It covers the history, the technology in depth, and it's practical uses in today's word in detail.