Tube Basics 101: What is a rectifier tube for?

In laymans terms please:

What is the function of a Rectifier tube (such as the 5AR4/GZ34 found in my tube preamp)?

Why/How would the Rectifier tube affect the sound created?

How would this differ from the function of a typtical Driver tube (such as a 6SN7, 12AX7, 12AU7)? Also, would a driver tube typically have more affect on the overall sound (i.e. Which tubes would you roll out first if you wanted to change the sound of your preamp?)

Also, what is a "Getter" tube?

Thank you for the reference. I never saw that wonderful article. Clever and informative. Thanks!
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I disagree.

CF is very important in the circuit of the topology you described! Try bypassing the CF (without replacing it with a transformer)in your preamp's output circuit and you will see how important it is on how the preamp will sound and how it will perform driving the load.

Just my opinion....
Isn't that like saying any average steering wheel will operate a car, but take it out and let's see how well the car operates?

Actually, the preamp Phono board uses only (1) 12AU7 and (1) 12AX7. I see how you thought it was (2) 12AX7s from the quote I inserted, but if you re-read it again you will see. Also, I double checked on the Modwright website that I linkd in my post above to be sure.

So given that, I'm still not sure if either/or (12AU7 and 12AX7)are cathode followers, as you say. Do you still think so? Does this change any recommendations for tubes to change?

Thanks everyone for all the info. I'll check out that article and probably have some more questions.