Amazon uses its own terms to refer to resources.
Amazon Machine Image (AMI) is an object that a VM can boot from. An AMI does not include the persistent storage needed, so it only includes the root of the bootable partition.
An instance store-backed AMI is copied to the root device of the instance prior to starting. Because the AMI is not changed by the running instance, any updates to the cloned root device is lost when the VM (instance) terminates.
An EBS-backed AMI is first copied to a persistent EBS block device. This way, changes to the EBS block device stays persistent.
EC2 (Elastic Cloud Computing) is a VM service. Most EC2 offerings are storage-free, requiring EBS to provide the mass storage for an instance.
There are many ways to purchase EC2 resources. For a 24/7 server, the “reserved” option is most cost effective. If paid 3-year and all upfront, the savings versus per hour on-demand can be up to 55%.
The t2.medium instance type has sufficient resource for a small web server that does not have heavy traffic and high processing power demand.
EBS (Elastic Block Store) is essentially raw block-based storage intended to serve the purpose of internal hard disk drives from the perspective of a VM. EBS is persistent across activation of instances.
EBS supports snapshots for back up purposes. Instead of replicating an entire EBS volume each time a snapshot is created, a snapshot is incremental to a prior one. This lowers the cost of backing up tremendously while retaining the ability to roll back to any snapshot taken.
That said, EBS snapshots is not for everything. For example, a running database cannot be backed up just by backing up files in the file system.
AWS EFS (Elastic File System) is, essentially, NFS. To connect to an EFS resource, NFS drivers are used.
The cool part of using EFS (as opposed to EBS) is that multiple VMs can use the same resource at the same time because it is a networked file system.
To configure a VM to use EFS, the ports needed for NFS should be enabled.