<reference path="..." />

/// <reference path="..." />

The /// <reference path="..." /> directive is the most common of this group. It serves as a declaration of dependency between files.

Triple-slash references instruct the compiler to include additional files in the compilation process.

They also serve as a method to order the output when using --out or --outFile. Files are emitted to the output file location in the same order as the input after preprocessing pass.