Retirement tax questions

So this is how it works for me: I have one 401k account through my employer, into which I may elect to contribute pre-tax, Roth, and after-tax amounts (it lets me select what % of my paycheck for each of those three amounts). So when you say stuff like "All distributions from the 401k are taxable", I'm not sure what you mean, because my Roth contributions and their earnings, for example, are not taxable.

 

I'm trying to get at a very nuanced question here, which I have not seen addressed on any forum, in any article, or even on the IRS's website. Given what I asked in my prior reply, with the scenario I gave, what part of what I said was incorrect? Or, is everything I said correct?