As a quick share, I have a routine of writing down the details of tasks that are accomplished, either for clients, or on my own projects.
Zip files are compressed files. Its usually a group of files that are gathered together and smashed down to make the overall file size smaller. They are commonly referred to as "zipped files." When zipped files are encountered, they need to be un-zipped, or de-compressed with a zip program. Windows users should be able to use 7-zip to un-zip files. Mac users may use stuff-it.