Looking up...
I saw her five minutes ago.
This means the speaker saw her five minutes before the current moment.
a period of time before the present
The meeting started ten minutes ago.
The meeting began ten minutes before the current time.
She left an hour ago.
She departed one hour before now.
Always used with a time expression (e.g., minutes, hours, days, years).
'Ago' is always used with a time expression (e.g., minutes, hours, days, years).
'Ago' comes after the time expression (e.g., 'five minutes ago', not 'ago five minutes').
'Ago' is always used with a time expression and refers to a specific time in the past.
From Middle English 'agoon', from Old English 'on' (on) + 'gean' (yesterday).
Always used with a time expression. Not used with 'before' (e.g., 'ago before' is incorrect).