While downloading files from this Portal site, you will undoubtedly discover the necessity of unzipping a file.
When someone "zips", or "packs" or "compresses" a file, they compress it; it is scrunched into a smaller pile of digital bits which makes the file
download faster on account of the new, smaller file size. It is also the only way to store certain file types on the server -
files such as .exe and .chm files. And so, before you can use these files they must be uncompressed.
Most computers have a built-in zip file handler. Try right-clicking on the zip file and see if "unpack" or "Extract All" is in the context menu.
If so, then your computer has the built-in handler. Otherwise, you might have to download one. There are many free zip-handlers
out there, so just install one on your computer.