Okay kiddo, do you know what a song is? It's like when you say words in a special way and it sounds nice and makes you happy. Now, a ragtime progression is kind of like the way the words in a song are put together.
Imagine you have a toy box with different colored blocks. Now, you want to make a nice tower with your blocks, but you need to think about what order to put them in so they look good. That's kind of like a ragtime progression.
It's when you put musical notes together in a special way to make a tune that sounds a little bit fancy and cheerful. This way of arranging the notes started a long time ago, when people used to play music on pianos in fancy cafes.
So just like how you carefully put your blocks together to make a pretty tower, musicians carefully put notes together in a ragtime progression to make a fun and upbeat song that you can tap your feet along with.