Zipping is a method of compressing a file eg. so that it is quicker to upload or download on the Internet. A program which can do this zipping and unzipping is Winzip. Most zipped files have the filename extension ".zip".
To handle a zipped file offered on the Web:
a. download it to your hard disk, e.g in c:\temp. Eg. you now have c:\temp\filename.zip.
b. unzip c:\temp\filename.zip (click here if you need Winzip). It will expand to its uncompressed size.
c. You now have c:\temp\filename.zip and c:\temp\filename.doc, orc:\temp\original\filename.lst or whatever the source filename was.
WordSmith can also make and read zipped wordlists, concordances, etc. The advantage is that they save hard disk space.