For getting a broad overview of the DeFi world, I recommend the video series hosted by Finematics. It’s broken down into Beginners (What is DeFi, DeFi Wallets, Smart Contracts, Uniswap, Lending/Borrowing), Apprentice Level (Liquidity Pools, Yield Farming, Yearn Finance, Yearn Vaults), and Master Level (Flash Loans, Sushi Vampire Attack, Ampleforth, NFTs, Layer 2 Scaling). Suggest going through these sequentially, starting at the beginning.
They’re generally 10 to 15 minute video segments with associated reading materials and example trades. If you go through the entire series, engaging with the materials and linked websites and examples, you’re likely to come out with a decent beginner’s perspective on the DeFi world, keeping in mind that things change fast in DeFi land.
Full disclosure, I haven’t gone through all segments, I’m more of a BTC hodler but am very interesting in how this space is progressing.