So imagine you and your friends are having a big contest to see who can do the best at different kinds of games. Maybe you have a running race, or a swimming race, or a game of throwing a ball into a basket. Everyone gets points for how well they do, and at the end you count up all the points to see who did the best overall.
The Olympics are like a giant version of that. Every four years, athletes from countries all over the world come together to compete in all kinds of different games (like running, swimming, throwing, jumping, and more). They get points depending on how well they do, and at the end of the Olympics, each country's points get added up to see which one did the best overall.
But here's the thing: the Olympics have been happening for a really long time - over 100 years! So even though the score gets reset every four years, we can still add up all the points that each country has ever earned in all of the Olympics put together. And that's what the all-time Olympic games medal table is: a big list of all the countries that have ever competed in the Olympics, ranked by how many points they've earned from top to bottom. The countries with the most points (or medals) are at the top, and the ones with fewer points are at the bottom.
It's kind of like a big history book that tells you which countries have done the best at the Olympics over the years. But remember - just like in your own contest with your friends, it's not really about winning or losing. What's important is that everyone tries their best and has fun competing!