Picture shows macOS High Sierra installed on HFS+ filesystem.
To determine OS X or macOS version, open Terminal.app and type:
To determine filesystem you are using now, type the following in shell:
mount | grep ‘ / ‘
This command will show you what disk partition is mounted as the root filesystem (/) and with what options – there is a bracket and first word inside should state ‘hfs’ or ‘apfs’.
How to upgrade macOS to High Sierra without filesystem change (HFS+ to APFS)