Elastic Block Store - AWS persistent storage that attaches to EC2 instances. Like having a dedicated hard drive that you can unplug from one computer and plug into another.
A database server uses EBS volumes to store data that persists even if the server needs to be replaced.
All are persistent block storage services designed to attach to virtual machines. They provide durable volumes for OS disks and application/data disks, with options for SSD/HDD performance tiers, snapshots, encryption, and resizing.