You're not alone, a lot of people don't understand the contract they sign (myself included). The first thing to know is that the contract isn't designed with you in mind. It protects the company by default. There are companies like secfi (https://www.secfi.com/) etc. that specialize in answering questions and have lots of free content
As for whether it can be "life-changing", yes. I know a number of people who are liquid/paper multimillionaires from startup equity. It's one of the few ways to build a ton of wealth. Hard to get this rich on salary alone
TLDR on equity is try to get a 10-year exercise window so if you leave the company before a liquidity event, you're not forced to come up with a ton of cash to buy them out or give them up: https://www.productlessons.xyz/article/how-stock-options-for...
Nearly all employees leave equity on table by virtue of not staying for 4 years, but many more simply can't afford to exercise which is far more disappointing