So you're working at this startup. Lets say it's worth $10 million. To make things simple, in this company, there are 2 people, the fucker, the CEO, the guy that started it all. He holds 90,000 RSUs, each worth $100, so $9 million, and the fuckee, you, who holds 10,000 RSUs, each worth $100, for a cool million.

Here's where the fucker fucks the fuckee, ie you. The company does a round, and then creates, out of thin air, a billion shares (1,000,000,000), and issues them to the new investors. Lets say the company reached unicorn status this round, which is to say a valuation of a billion.

Holy hell a billion! But wait now there's 1,000,100,000 total shares out there, and the valuation of a billion, divided by the new shares, means that each share, of which you only have 10,000 of, is now worth just under one dollar.

That's right, your $1 million just turned into $10,000. Which isn't nothing, I'd love to come across a random $10k I didn't know I had. But that's just, like, one really nice vacation for you and the kids, which you haven't seen enough of because you've been working so hard at this startup, and not, like, a college fund for the kid that's showing aptitude at engineering and that you were hoping was gonna go to MIT.

Dilution is inevitable, there's no avoiding it. The scenario I presented is just to show you an example of how dilution fucks you. If things go well, would you rather have 10% of $1 million or 0.1% of $1 billion?

For more, it depends on how you like your information. ChatGPT's got stuff like ISOs vs NSOs pretty well covered, Investopedia's got a lot of good stuff if you'd rather it that way.