Damage in Chronicle X is usually caused via Attacks, and non-Critical damage can potentially be prevented by various defences. Any damage that is not prevented will normally cause loss of that much health for the target of the damage, if the target is a Hero or an Alien Unit.
If the target is an object, the object is normally destroyed if it receives two or more normal points of damage, or one critical damage.
Health
Health in Chronicle X is a stat of Models, with a starting value given by their stat card or stat board.
For Heroes, the Health is given by the maximum value of their Health Dial on their Hero Dials Board. It is normally 8. When a Hero receives damage, the Health Dial is turned to a lower value, which also causes two of the other stats the Hero has to change.
For Alien Units, the Health is tracked by putting Wound tokens next to the Unit on the Mission Map; or alternatively, if there is only one such Alien Unit in play, the tokens can be put on the Alien Unit card instead. Some Units can also lose Health by losing members of the Unit.