HDX Double-Hop:

This is formerly known as ICA Pass-Through.

User logs into first storefront store on end point device receiver and initiates connection to desktop or server virtual delivery agent. This Citrix desktop or server virtual delivery agent has receiver installed in it and has second storefront details. When user launches an application from Citrix virtual desktop which is on second storefront, he logs into second storefront server and launches the application.

Disk drives connected to first Citrix virtual desktop, are not available in second virtual desktop or application if client drive disable policies are applied on the first citrix virtual desktop. When this policy is applied, first VDI doesnt map your laptop drives, and also do not show or map drives in the app/vdi launched from the first vdi. If you still want to access the first VDI drives in the app/vdi opened from the second Citrix portal, you need to set the NativeDriveMapping to True in registry on the first vdi.

Benefits include:

Resource intensive applications, applications with multiple versions, or applications with known compatibility issues can be accessed from second hop, having no performance issues on first hop Citrix desktop. It also gives an improved desktop image management. This can also minimize security risk as your applications are accessed from organization Citrix virtual delivery agent which is in first hop.

Note: Only caveat is you should have different storefront servers for first hop applications and desktops and second hop applications and desktops. If not auto launch or reconnect to workspace applications will cause an issue. Additional infrastructure might be needed.

If we have user/device license type, user can connect to multiple devices and a VDI(in second hop) can have multiple users.

Check out this article to deploy double hop environment in netscaler: https://docs.citrix.com/en-us/netscaler-gateway/12/double-hop-dmz/ng-double-dmz-how-it-works-con.html