In pictures: Taking apart Hewlett-Packard's Prolia...
The UID light is similar to the one on the front. The back light allows users to easily identify a server when going between the back and the front of the rack.<br /><br />The iLO2 port is used to remotely access the server. It provides SSH (secure shell) and HTTPS access to diagnostics, and allows remote access to a virtual serial port for those want console access.<br /><br />The back access ports are similar to the ones on the front of the server. This allows you to plug in a monitor/mouse on the back if this is more convenient for the system administrator.
In pictures: Taking apart Hewlett-Packard's Proliant DL380 G5 server