To create a compressed file, either Control-click on the file and choose Create Archive (which is Apple-speak for “make a compressed ZIP file”). Or you can click on a file, then go to the Action menu (the button that looks like a gear up in the Finder window’s toolbar), and choose Create Archive from there. Either way, it quickly creates a new file, with the file extension “.zip.” This is the compressed file. You can also compress several different files (like three, for example) into one single archive file — just Command-click (or Shift-click contiguous files) on all the files you want included, then choose Create Archive of X Items from the Action menu. A file will be created named “Archive.zip” (that’s it!). By the way, if someone sends you a ZIP file, don’t sweat it — just double-click it and Tiger will automatically decompress it.