Outlook is supported both on Windows and Mac OS. While there is only one version of Outlook for Mac - Outlook 2011, there are several Outlook for Windows versions.
Each version has a different interface, but you can also find out what client you're using by viewing About Outlook information:
- File > Office Account > About Outlook > Outlook 2016
- File > Info > Office Account > About Outlook - Outlook 2013
- File > Help - Outlook 2010
- Help > About Microsoft Office Outlook - Outlook 2007/2003