Horizon 7 provides a streamlined approach to delivering, protecting, and managing Virtual Desktop Infrastructure (VDI) and applications while containing costs and ensuring that end users can work anytime, anywhere, across any device.

The Horizon for view part (related to VDI) is tightly integrated with VMware vSphere, requiring both vCenter Server (that is managed by the View Manager and is needed to perform provisioning and VM management) and ESXi (that is used to host the VDIs). There are some exceptions, such as if you are using manual pools of dedicated (and pre-provisioned) VMs. 

Also, note that there are now some new offers, such as Horizon Cloud on Microsoft Azure (https://blogs.vmware.com/euc/2017/10/vmware-horizon-cloud-on-microsoft-azure-now-available.html).