Traditional IRAs contain post-tax dollars (you make deposits using money you have already paid taxes on).
Traditional IRAs grow tax-free.
Traditional IRA accounts are taxed as income when you withdraw money. If you make the unfortunate mistake of withdrawing before age 59-and-a-half, you'll have to pay an additional 10% penalty on top of the taxes! (Do not ever do this if you can avoid it)
Vanguard is never a bad choice.
Robo-advisors are good if you are just getting started, or if you want a hands-off approach.
Index funds are the name of the game.
Target date funds are a great way to have a mix of index funds and bonds that gradually shifts towards the safety of bonds as you get older.