Ok, let's pretend you have a bunch of toy cars, and you want to line them up in a particular order.
First, you pick a car and call it "vi". This car is going to be the 6th car in the line. Then, you look for the car that comes after it and call it "ii". This car is going to be the 2nd car in the line. Next, you find the car that comes after the "ii" car and call it "v". This car is going to be the 5th car in the line. Finally, you look for the car that comes after the "v" car and call it "i". This car is going to be the 1st car in the line.
So, the order of the cars in the line is "vi-ii-v-i".
But what do these numbers mean? Well, in music, these numbers represent different chords. A chord is when you play a few notes together that sound good. And vi, ii, v, and i are special chords that are often used together because they sound really nice and make a song feel complete.
Each chord has its own unique sound, just like each car looks different. When you put them in a particular order, it creates a special sound that many people like to listen to.
So, in the vi-ii-v-i progression, you start with the vi chord, then move to the ii chord, then the v chord, and finally, the i chord. It's like driving the cars in a specific order to create a special musical feeling.
Many songs and melodies are created using the vi-ii-v-i progression because it sounds pleasing to our ears. Just like playing with toy cars is fun and exciting, listening to music with these chords can make us feel happy and want to dance or sing along.