Can someone tell me what exactly is being said here?

Question:

Can someone tell me what exactly is being said here?

It's the explanation of how high each voice type is suppose to go. But I don't understand what G3 is or below C4 and so on down the line. Could someone please explain this to me? Thanks

Soprano
High female voice, G3 (below middle C4) to F6 above high C6 although anywhere above high C can be included.

Coloratura
A singer, usually soprano, who sings ornamental passages in music - C4 to F6 or G6 above high C6

Lyric Soprano
Warmer middle sound - Bb3 below middle C4 to high C6 or D6

Spinto Soprano
Usually a thicker sound with more edge and volume but with the same range as a the Lyric Soprano

Dramatic Soprano
The loudest and lowest with cutting power - low Bb3 or A3, to a pushed high C6

Mezzo-Soprano
Middle female voice with dark quality, Low A3 or G3 (below middle C4) to at least high C although it is not uncommon for high A6 or Bb6 to Eb6 above high C6

Best Answer - Chosen by Asker: When they say C4, they mean it's the fourth C on the piano, starting from the left, or lower, end. If you can look at a piano (not a keyboard) you can figure it out.