<prompt> Human: Heres How I understand it.Traditional - can be a 401k or IRA, means the contributions are put in tax free a tax deduction, lowers your taxable income, the earnings grow tax free, and you pay taxes when you take the money out in retirment.Roth - can be a 401k or IRA, means the contributions are taxed when you put them in, but the earnings grow tax free and your withdrawals in retirement are tax free.401k - can be Traditional or Roth, this is an employer sponsored retirement plan. You contribute money, the employer has a broker than manages your investment. Annual contribution limit is 18.5k in 2018.IRA - can be Traditional or Roth, this is an Individual Retirement Account, you pick your broker, funds, stocks, bonds, whatever. The whole thing. Annual contribution limit is 5.5k for 2018, I think.401ks and IRAs have limitations based on your income, but Im not sure how those work.Do I have it down right? Im asking because a lot of times when I read threads on personalfinance and some other financially oriented subs and other articles, it seems like everyone mentions 401k in the Traditional sense and ignores that Roth 401ks exist. Is that just me or is it actually like that? Are Roth 401ks not commonly offered? Are they relatively new?  <response>: You are correct except for one thing. In a 401k the employer has a broker, but usually they do not manage your investments, you do. However, the broker usually only offers a selection of investments for you to chose from, instead of all the investments in the market. Sometimes the selection offered is not as good as you could find in the market more limited selection, funds with higher expense ratios.You are correct that Roth 401ks are often ignored. They are relatively new, and, although more and more common, probably more than half of 401ks still dont offer them. 