When you input a URL such as https://steamcommunity.com/sharedfiles/filedetails/?id=1111111111 (or ID such as 1111111111) it will download it from steam (using Steam Workshop Downloader API) into the current folder as a ZIP. And it will decompress the contents into the desired folder before deleting the remaining ZIP.
This program may need Administrative Permissions (Run as Admin) to be able to access folder that are being used by other programs. Otherwise it will prompt and error saying "No Permission" or it will not allow you to browse the the desired folder.