Elastic Block Storage
Think of it as virtual disk in the cloud
Allows to create storage volumes and attach them to EC2 instance.
Once atttached, you can create a file system on these volumes (called root device volume), run a db, or use as a simple block device.
EBS volumes are placed in a specific availability zones, where they are automatically replicated to protect you from the failure of a single component.

EBS Volume Types

SSD

For general use, balances both price and performance.
Ratio of 3 IOPS per GB with upto 10,000 IOPS and the ability to burst upto 3000 IOPS for extended periods of time for volumes at 3334GiB and above.
Provisioned IOPS SSD (IO1)
Designed for I/O intensive applications such as large relational or NoSQL db.
Use if you need more than 10,000 IOPS.
Can provision upto 20,000 IOPS per volume.
Throughput Optimized HDD(ST1)
Big Data
Data Warehouses
Log Processing
Cannot be a boot volume

Lowest cost Storage for infrequent accessed workloads.
File Server
Cannot be a boot volume.
Magnetic (Standard)
Legacy
Lowest cost per GB of all EBS types.
Bootable storage.
Ideal for workloads where data is accessed infrequently, and low cost is important.