AWS line item type

Type	Comment
Unblended	(Default) Unblended costs represent your usage costs on the day they are charged to you. In finance terms, they represent your costs on a cash basis of accounting. For most of you, this is the only cost dataset that you will ever need.
Amortized	view costs on an accrual basis rather than a cash basis. This cost dataset is especially useful for those of you who have purchased AWS Reservations such as Amazon EC2 Reserved Instances.
Blended	Blended costs were originally created to support customers who chose to consolidate their billing under a single paying account. Nowadays, these costs are not used frequently due to the way that they are calculated.

Reference

• Understandig your AWS Cost Datasets: A Cheat Sheet