This will be applicable for services with the rate that looks like this:
For example, it could be
RDS (Relational Database SErvice), or
EBS (Elastic Block Store).
The rate shown above is the rate for RDS of instance type
Provisioned IOPS SSD (io1) Volumes.
If you have created the instance (or could be created by another service), but not sure what that means to your bill. Chances are you might not need it, or otherwise, be prepared for a higher bill amount.
How the bill are calculated for provisioned IOPS-month type of instance:
$0.11 * 1000 IOPS * number of hours
= $110 for 1 month
= $3.67 for 1 day
That's for 1000 IOPS for an instance.
Also, please take note that:
So if you enable an instance of 8000 IOPS of io1, but only used a bit of it, you will still be charged for
$0.11 * 8000 * number of hours
$0.138 per GB-month
So, if you are not sure, probably a General Purpose SSD (gp2) volume is your right choice.
Refer to the EBS pricing for another example. (the IOPS-month rate is applicable for RDS as well)