The hierarchy is small enough to memorise and precise enough that the exam will punish a loose reading of it.
Regions
A Region is a named geographic area containing multiple Availability Zones. Regions are isolated from each other by design: nothing replicates between them unless you configure it to.
Choosing a Region
Compliance first, then latency to your users, then service availability, then price. Newer services do not launch everywhere at once, so the third check catches more people than expected.
Availability Zones
An AZ is one or more discrete data centres with independent power, cooling, and networking, connected to sibling AZs over low-latency links. Spreading across AZs is the standard answer to “how do I survive a data centre failure”.
Edge locations
CloudFront’s cache sits at edge locations, of which there are far more than Regions. Route 53 and AWS Global Accelerator use the same footprint.
The specialised zones
Local Zones place compute close to a metropolitan area for latency-sensitive workloads. Wavelength Zones sit inside telecom providers’ 5G networks. Both are extensions of a parent Region rather than Regions in their own right.
Direct Connect
A dedicated private link between your premises and AWS. It is not part of the Region hierarchy, but questions about consistent network performance usually want it as the answer.