@babel/plugin-transform-numeric-separator allows Babel to transform numeric separators (underscores) in JavaScript numbers. This enhances code readability by visually grouping digits in large numbers, for example, 1_000_000 instead of 1000000. The plugin removes these separators during compilation, ensuring compatibility with environments that don't natively support them. This plugin simplifies working with large numeric constants, improves maintainability, and helps prevent errors from misreading long numbers.