THE CAP TABLE YOU DIDN'T NOTICE YOU WERE BUILDING

Summary from the TLDR Founders newsletter

A SAFE is a promise where an investor gives a company their money, then when the company finally sells stock at a real price, the investor gets shares, usually at a discount or capped at some valuation as a reward for going first. There's no interest, due date, or anything owed if that day never comes. For founders raising a small amount quickly, it's a good trade. For investors, the worst-case percentage locks the moment they sign.