It's an official Google Chrome extension by Free Download Manager developers. The sole purpose of this extension is integration with Free Download Manager. FDM is a fast and reliable download manager and accelerator that improves your experience with downloads and helps you organize them in an easy manner.
If you want to help us make Free Download Manager (or this Chrome extension) better – you are always welcome on our forum where you can post bug reports, feature suggestions, and ideas, as well as get support for any issues you stumbled upon with FDM: https://www.freedownloadmanager.org/board/
Note: Windows, Mac and Linux! Requires FDM to be installed to work properly.