The chronology of the universe is like a timeline of when different things happened. Starting at the very beginning, the universe was born about 13.8 billion years ago in a cosmic event called the Big Bang. After the Big Bang, the universe quickly expanded and became filled with particles, like protons and neutrons.
As it continued to expand, matter formed galaxies, stars, and planets. These galaxies, stars and planets formed and changed over millions and billions of years, and new planets and stars were created by the process of the stars in galaxies burning the gas and dust around them.
Jump ahead to the present day and we have a universe that is much different than it was in the beginning. Stars and galaxies are still forming, but life also exists in the universe. Plants, animals, and people all exist in the universe.
The chronology of the universe is like a timeline of how the universe changed and evolved over billions of years. It's constantly changing and evolving even to this day!