The Chargin' Targe replaces your primary weapon slot, preventing access to sticky bomb launchers, but cuts all fire damage in half, and explosive damage by 40%.
It is not used in a weapon slot, but simply sits on your left arm while using your grenade launcher or melee weapon. A right click with either of these weapons will send you screaming straight forward in a long burst of speed.
While charging a meter will drain from full to empty over the course of the charge, and changes from green to orange to red.
These colors represent your final damage bonus if you attack during the charge with a melee weapon, which will end it. Green is no bonus, orange is a mini-crit, and red is a full critical swing.
This meter slowly fills up afterward to represent the cool down until your next charge which is around 12 seconds.
You also do damage with the shield itself if you make contact with an enemy at the end of the charge. Base damage is 50 plus an additional 10 for each head you've severed with the Eyelander. (5 head bonus maximum)
The Eyelander on it's own does not deal any critical hits. When both The Eyelander and The Chargin' Targe are equipped it is able to deal crits when used together with the Targe's charge attack.
The Chargin' Targe is awarded for achieving Milestone 1 (Complete 5 of the Demoman achievements)