VMware ESXi 4.0 Update 1 and Later Installable with vCenter Server 4.0 Update 1 and Later

vSphere Basic System Administration : Getting Started : Using the vSphere Client : Manage vCenter Server Plug-Ins

Manage vCenter Server Plug-Ins
After the server component of a plug-in is installed and registered with vCenter Server, its client component is available to vSphere clients. Client component installation and enablement are managed through the Plug-in Manager dialog box.
The Plug-in Manager enables users to do the following: