Okay kiddo, there are a bunch of grown-up people who really like to ride bicycles. They like to ride them a lot, and they like to study the history of people riding bicycles in lots of different countries.
These grown-ups decided to have a big meeting, known as a conference, so they could talk about all the cool stuff they've learned about cycling history in different parts of the world. They'll talk about how bikes have changed over time, who the most famous cyclists are, and even how people used to race bicycles in big groups.
They'll also talk about the importance of bicycles in different cultures, and how they use bikes for things like transportation, sport, and leisure. Some of the grown-ups might even bring pictures or videos of old bicycle races, to show other people who weren't there.
Basically, the international cycling history conference is just a big meeting where lots of bike-loving grown-ups get together to share stories, information, and have some fun too.