The 'Dedicated Servers' menu allows you to add/manage a Dedicated Server to your account. It also offers the ability to add an admin user to the server which allows you to run commands as sudo/root.
The Dashboard page shows a list of Dedicated Servers for this account.
An admin user is given full root access to the Dedicated Server via the sudo command. These are special users with full access to the server.
Be careful when you’re using an admin user as you will have the ability to disrupt system settings which could disable your sites or server. Make sure you know what you’re doing when using an admin user.