Don't deny it. You need money, to buy food, or more importantly, botch a wall shelf.¹ The Man wants to take it for roads or research or whatever. So, to keep as much of it as possible, you optimize your taxes. Greedy pig.

I'm not giving financial advice. I'm not giving tax advice. I'm merely giving unsolicited investment thots, to an imaginary audience that I'm assuming makes enough to invest long-term while covering reasonable expenses short-term.

Normally, you pay taxes before buying an investment; let's call this taxes on contributions. Hopefully, the investment grows in value. Then normally, you pay taxes on the difference in value after selling the investment; let's call this taxes on withdrawals. In certain tax-advantaged accounts, you don't need to pay the taxes on contributions and/or the taxes on withdrawals.

For a health savings account (HSA), you effectively do not pay taxes on contributions and do not pay taxes on withdrawals for medical expenses. With medical inflation outpacing general inflation, you'll probably need it. Otherwise, you can withdraw as normal taxable income during retirement, so you might hold off on spending from your HSA until retirement.

For a Roth individual retirement account (IRA), you only pay taxes on contributions and do not pay taxes on withdrawals during retirement. If you make more income than allowed to contribute directly to a Roth IRA, you can contribute after-tax to a traditional IRA and immediately convert that into a Roth IRA. If you've previously made pre-tax contributions to the traditional IRA, you'll need to consider the pro-rata rule for taxes on conversion, though you still won't need to pay taxes on withdrawals during retirment from converted Roth IRA funds.

If your employer offers 401(k), lucky you! For a Roth 401(k), you only pay taxes on contributions and do not pay taxes on withdrawals during retirment - who would've guessed! You might prefer a Roth 401(k) over a traditional 401(k) because like Roth IRAs, Roth 401(k)s no longer have required minimum distributions (RMDs). Some 401(k) plans, like my current plan, also allow you to contribute after-tax to a traditional 401(k) and convert that into a Roth 401(k), which should sound familiar. I think the pro-rata rule still applies? Talk to an expert, since I'm merely giving unsolicited investment thots as not-quite-an-expert.