The larger a file is, the longer it takes to download. So some files online are compressed ”converted into smaller files ”to cut the download time. After downloading, you must decompress a compressed file to restore it to its original size and use it.
Also, most application programs are made up not just of one fat file, but of a collection of program and data files. A single compressed file can pack together many separate files, so they can all be downloaded together in one step. When you decompress a compressed file containing multiple files ”which is sometimes called an archive ”the files are separated.
Several forms of compression are used online, but most compression programs create archive files that use a format called Zip. A Zip file uses the extension .zip , and it must be decompressed ” unzipped ”after downloading before you can use the file or files it contains.
You need a special program to unzip Zip files. If you don't already have one, the most popular shareware unzippers
After installing an unzipping program, you can decompress any Zip file by opening the program, choosing the Zip file you want to decompress, and then choosing Extract from a toolbar or menu.