Question about Variables (Mike Dane's Python Beginner Tutorial)

Hello there, I’m totally new here.

I started to learn Python through Mike Dane’s YouTube video (which is in the freeCodeCamp channel) and I didn’t understand the variables he uses in the “Build a Translator” section (here is the timestamp and link to the video

He wrote:

def translate(phrase):
    translation = ""
    for letter in phrase:
        if letter.lower() in "aeiou":
            if letter.isupper():
                translation = translation + "G"
                translation = translation + "g"
            translation = translation + letter
    return translation

print(translate(input("Enter word/phrase: ")))

My questions are:
1 - Is the variable ‘letter’ a “set Python variable” that looks as each character and changes them? Or is ‘letter’ just a variable…? I don’t understand how is “sees” the actual letters in the string and translates them.
2 - I also did not understand how the “letter.lower()” will understand that the character regardless of being upper or lower case will still be “read” by the program.

Forgive me for the basic vocabulary to try and explain my question. If it isn’t clear I can try to elaborate.

Thank you.

It helps to format your code correctly–

use backticks for the part where your code is.

As for your question…
phrase is likely a string, like “pizza”.

When you do for letter in phrase it iterates through each letter of phrase.

So on the first iteration, letter would be ‘p’, then ‘i’, then ‘z’ ect…

The point behind .lower is so that if phrase was “PIZZA”, it would first lower case the individual letter., and then check if that letter was in the string ‘aeiou’.

I’ve edited your post for readability. When you enter a code block into a forum post, please precede it with a separate line of three backticks and follow it with a separate line of three backticks to make it easier to read.

Please use the “preformatted text” tool in the editor (</>) to add backticks around text.

See this post to find the backtick on your keyboard.
Note: Backticks are not single quotes.