The provider that offers A-Z service will give you services to countries that start with A all the way to Z.
In other words, worldwide service.
May be someone could explain how is that it ended up being called A-Z on the first place.
Other terms:
30/6 Means that you will be charged 30 seconds minimun when the remote party picks up the line, and blocks of 6 seconds after the initial period.
PDD Post dial delay: How long will you be waiting for a ringback or a busy indication after you send the call to the provider.
Related to old equipment on third world countries, where the call need to be converted from digital to analog to be sent to the final destination.
ASR An average of how many calls sent to this particular route get a conection, versus the ones that do not go anywhere. The higher the merrier.
Is consider a good indication of how good is the route.
Does not matter how good the route it is, some countries do not have good ASR does not matter what carrier you use.
At leat now you will confused by the information, not the lack of it.
Best regards.