most startups don't offer actual equity even though that's what everyone calls it. they offer options. the idea is that the options you'll receive will have a strike price much lower than what the stock will be worth in future funding rounds or when the company is acquired or IPOs. the vesting schedule defines when you can start to exercise those. typically you'll receive 25% of your options after the first year, then the other 75% will vest every month after.

and yes, liquidity in a private company is always going to be an issue.

all of this is why I tell everyone that their options are worthless right up until they're not. anyone who's burned out or looking at a new opportunity shouldn't include them in their decision making process.