Asia First is a term that refers to the idea that Asia, which is a large continent made up of many countries, was the first place where important things happened a very long time ago. This includes things like the invention of writing, the development of religions like Buddhism and Hinduism, and the creation of many great empires, such as China's Han Dynasty and India's Mauryan Empire.
Basically, people who say "Asia First" are trying to highlight the many important achievements and contributions that people from Asia have made throughout history, and how these things have impacted the whole world. It's kind of like saying "Asia was great a really long time ago, and we should remember and recognize that."
Of course, it's important to remember that other parts of the world, like Europe, Africa, and the Americas, also have their own rich histories and have made important contributions to the world. But Asia First is a way of celebrating and appreciating the unique and important things that people from Asia have done throughout history.