Areas and locations
Cloud providers run data centres around the world. A region is one geographic area; an availability zone is a separate group of data centres within it. If one zone has a power or network problem, another may keep running.
When setting up a virtual machine or database, a team chooses a region and sometimes a zone, depending on the service.
Why location matters
Putting services near users can make them respond faster. Running copies in different zones can keep an app available if one zone fails. Using different regions can help with wider outages, but costs more. Teams may also have rules about where they can store data.