You aren’t dumb. There are even major social media influencers in the crypto space who have tens of thousands of followers but don’t understand the difference between market cap and liquidity. It’s important to understand if you don’t want to get rekt on a memecoin though, and it and can be totally different to market cap or volume. The price impact (very commonly confused with slippage which is a little different) of any buys or sells depends entirely on liquidity.