Okay kiddo, so you know how sometimes grown-ups get together to talk about important things and share ideas? Well, in the year 1920, a bunch of grown-ups from countries all over the world got together for a conference in a place called Spa, in Belgium.
Now, these grown-ups were all talking about something called "reparations." That's when one country has to pay money to another country because of damage or harm they caused during a war. See, there had just been a big war called World War I, and some of the countries that had fought in the war were now trying to figure out how to pay for all the damage they had caused.
At this conference in Spa, the grown-ups were trying to decide how much money one particular country, Germany, should have to pay. Germany had been one of the main countries that had started the war, so they were responsible for a lot of damage.
But the problem was, Germany was really struggling to pay all the money they had already been told to pay. So the grown-ups at the Spa conference were trying to figure out if they should make Germany pay even more, or if they should give them a break and let them off the hook for some of the money.
It was a really tricky problem, and the grown-ups spent a lot of time arguing and debating. In the end, they decided to reduce the amount of money that Germany had to pay, but not by as much as Germany wanted.
And that, my dear five-year-old, is the story of the Spa conference of 1920 - a meeting of grown-ups trying to solve a big problem about money and reparations after a big war.