Okay kiddo, so you know how we use numbers like 1, 2, 3, and 4 to count things? Well, a long time ago the ancient Romans had a different way of counting. They used letters from their alphabet to represent numbers.
So when we see a number like 5, the Romans would write it as V (which is the Roman numeral for 5). And if we wanted to count up to 10, they would write it as X (which is the Roman numeral for 10).
Now, fast forward to today, and we still use Roman numerals in some fancy places like on clocks, in movies, or on important documents.
But, we've also found a way to use Roman numerals to help us understand different types of music, and that's called "Roman numeral analysis."
Basically, in music we use Roman numerals to represent different chords (which are groups of notes played together). For example, the chord made up of the notes C, E, and G is called a "C major chord."
And when we write out the chords for a song using Roman numerals, we use capital letters to represent major chords (like C) and lowercase letters to represent minor chords (like a minor chord made up of the notes A, C, and E would be written as "a").
So let's say we're looking at a song that starts out with a C major chord, and then switches to an A minor chord. We would write that out using Roman numerals as "I (which means C major chord) - vi (which means A minor chord)."
This helps musicians understand the structure of the song and how the chords are related to each other. Kind of like a secret code for music!