Draw-game explainers
The draw games look simple from the counter: pick numbers, wait for the draw. What's behind them is a prize chart, a set of odds and a pile of rules about claiming and tax. These pages lay each one out.
Where I'd start
Start with the game you actually play. Powerball and Mega Millions each get the full treatment: the ticket, the prize chart, the odds and what a ticket is worth on average. I'd read the prize chart even if you never look at the jackpot odds, because nearly every winning ticket is a small prize, and that's the part people skip.
Then the parts that matter only if you win. Taxes explains what's withheld and what's owed, jackpot claims covers how a big prize is actually collected, and lottery scams lists the tricks aimed at people who think they've won. I'd read that last one even if you never buy a ticket.
The rules for claiming, taxes and online sales are set by each lottery, so where these pages give one lottery's rule as an example, they say whose it is.