Op is running Ubuntu 16.04 which is Linux Standards Base (LSB) - there are changes to the way Ubuntu sets up apache. If Op; had experience with Ubuntu earlier versions, things have changed.
Please see:
The section on Server Configuration and especially read about 'sites-available' and 'sites-enabled' in that section.
One shouldn't see a 'html' directory listing unless Op has changed default config. That directory should be 'document root'. IF anything, Op should have seen a 'moodle' directory.
Suggest, if Op has made any changes to conf files for apache, revert them back and read about sites-available/sites-enabled.
'spirit of sharing', Ken