The Veeam PowerShell Toolkit is automatically included when installing either Veeam Backup & Replication or the Veeam Backup & Replication Console.
Starting with Veeam Backup & Replication 11, the Veeam PowerShell Toolkit is a PowerShell module instead of a snap-in.
Scripts containing the command "Add-PSSnapin VeeamPSSnapin" will fail and display the error:
No snap-ins have been registered for Windows PowerShell.
From the Veeam Backup & Replication 11 What's New PDF:
PowerShell module — By popular demand, we switched from the PowerShell snap-in to the PowerShell module, which can be used on any machine with the backup console installed. We also no longer require PowerShell 2.0 installed on the backup server, which is something many customers had problems with.