There are four types of damage that a character will encounter in combat: Energy, Ballistic, Slashing, and Blunt
Any damage source that does not rely on kinetic energy or chemical/biological manipulation to damage its target. These sources primarily involve high amounts of heat, such as provided by fire, plasma, and laser. Electricity and radioactive decay are also considered to be sources of Energy Damage.
These damage sources rely on kinetic energy and mechanical advantage to deliver focused amounts of destructive force. In general, anything sharp flying through the air at high velocity is considered to provide Ballistic Damage. These include bullets, arrows, spears, shrapnel, African AND European Swallows, and a host of other similar sources that pierce their targets.
Sources of this kind of damage rely on mechanical advantage and the precise application of force from relatively massive objects. Objects that cut and slice, and that are wielded by an individual, are primarily responsible for this kind of damage. Pieces of sharp debris, more massive than shrapnel, would fall under this category.
Any kind of damage that involves force without the use of a blade or point. Everything from getting crushed against a wall, to being clubbed to death, to being caught in an explosion is covered by this damage type.