Failover Engine query

1.        What failover engine (FOE) and how it works? (Does it sends hello message)
2.        Do we need two databases for this product?
3.        Does it requires install all Orion modules in both primary and secondary boxes?
4.        Does trap  and syslogs goes to both databases and Orion boxes?
5.        Can we keep primary and secondary box in different location? If so then what should be bandwidth and latency required?

Thanks,

Sanjit