This VS Code extension does one and only one thing: it provides syntax highlighting support for Drupal specific file types, such as .module, .inc, .theme etc.
If you want, you can specify the syntax highlighting rules for specific filetypes in VS Code's settings, but I think having an extension is more conveninent because it is far quicker to just install it rather than having to manually add several filetypes to your settings.json (some of those file extensions are not frequently used and might be easily missed).
- .engine
- .theme
- .install
- .inc
- .make
- .module
- .profile
- .test
- .info