Is it possible to use services in different regions in AWS

1. Is it possible to use say service A in region X and service B in region Y in AWS. Is it recommended.
2. What advantages do we get when we design our application like this , (if any)
3. Going through this and this, i have learnt that we should use regions to avoid latency issues and use Availability Zones to replicate the infrastructure thereby achieving robustness. Is my understanding correct ?