Azure SQL Auditing

I am trying to fill some gaps in my understanding of auditing for Azure SQL

1) Why enable server auditing? I see no value proposition (Azure SQL)

2) when I enable database auditing does it automatically start auditing everything?

3) If 2 is a yes, can I create an audit specification to audit only select tables before enabling to avoid log ingestion which I don't require?

4) does enabling audit logging for a database automatically start filling logs or does that merely create the connection to the storage

Thanks for any answers

Peter