These files are compressed in 'zip' format and should be able to be expanded again using compression software like MacZip (Macintosh) or WinZip (Windows), which are available as shareware or came free with your system.
These files are compressed in 'BinHex' format and should be able to be expanded again using software like Stuffit Expander (Macintosh) or PKZip (Windows) which are available as shareware or came free with your system.