Zipping a file creates a compressed version of the file that is smaller than the original file. The zipped version of the file has a .zip file extension. For example, if you zip a Microsoft Office Word document called Christmas_2008.doc that is 6.5 megabytes (MB) in size, the file created, Christmas_ 2008.zip, is reduced to 2.5 MB. Compressing files was more important in the days of dial-up internet access, when it could take forever to send or receive a large file. With broadband, the need to zip files has reduced. If you receive a .zip file then do a right-click with your mouse and you should see an option to extract the compressed file. Zip files are often used to transmit viruses, so be careful; don't open attached files from strangers.