Data versioning refers to saving new copies of your data when you make changes so that you can go back and retrieve specific versions of your files later.
In Level 0, the data lives on the filesystem and/or object storage and the database without being versioned.
In Level 1, the data is versioned by storing a snapshot of everything at training time.
In Level 2, the data is versioned as a mix of assets and code.
Level 3 requires specialized solutions for versioning data. You should avoid these until you can fully explain how they will improve your project.