The Macbook "Archive Utility" app can't open certain files, and it really limits what you can use and download online. The "Unarchiver," unarchives these files, and many, many more formats compared to Archive Utility. It can also unarchive foreign files formats and character sets. This is useful for downloading files from other countries, which I often do. There is a supported file list that the unarchiver has.
You can get this application from the apple store, however, I would discourage it as it limits a lot of what the app can do. I would highly recommend downloading it from its site. Go to the Unarchiver webiste. Then click "Download The Unarchiver". Save the zip file and open it. Once its down extracting, drag the icon into applications. Now you are all set, and can set your default extractor to the Unarchiver.