An Amazon EC2 Dedicated Host is a physical server that is fully dedicated for your use.

Dedicated Hosts provide visibility and control over instance placement and they support host affinity. This means that you can launch and run instances on specific hosts, and you can ensure that instances run only on specific hosts. For more information, see Understand auto-placement and affinity.

Dedicated Hosts provide comprehensive Bring Your Own License (BYOL) support, and that’s why they’re usually used. They allow you to use your existing per-socket, per-core, or per-VM software licenses, including Windows Server, SQL Server, SUSE Linux Enterprise Server, Red Hat Enterprise Linux, or other software licenses that are bound to VMs, sockets, or physical cores, subject to your license terms.

You don’t pay for instances you launch on the host, instead you pay for the whole host:

An host is designed to run a single instance type, while size can usually vary. For example, on a A1 host (1 socket, 16 cores) you can run:

Some hosts require to declare in advance the size for ALL the instances. Nitro-based hosts don’t have this limittation. You can mix sizes.

RHEL, SUSE Linux and Windows, RDS are not supported. (?)

You can’t use Placement Groups.

Dedicated hosts can be shared with accounts in the organization using the Resource Access Manager (RAM). The other accounts can only see instances they create while you can view but cannot control instances they create.