Difference between ‘ before ‘ and ‘ ago ‘
The word ‘ ago ‘ is used as an adverb and has one primary definition. It is used with past tense and a time expression to count back from the present. While the word ‘before ‘ can be used in three different ways , as a preposition , a conjunction and an adverb.It is used with a past tense to count back from a past moment.It can also be used to mean ‘ at any time before now/ then’. With this meaning , it can be used with both present and past perfect tenses.
1. She left home 10 minutes ago .
2. Have you been here before ?
3. He had to leave before his appointment time was due.