Take from http://www.vmware.com/support/developer/vcli/

The vSphere Command-Line Interface (vSphere CLI) command set allows you to run common system administration commands against ESX/ESXi systems from any machine with network access to those systems. You can also run most vSphere CLI commands against a vCenter Server system and target any ESX/ESXi system that vCenter Server system manages. vSphere CLI includes the ESXCLI command set, vicfg- commands, and some other commands.