A wound is an underlying psychological place of pain or negative belief about yourself or the world.
A wound is caused by an incident or series of incidents or a relationship in childhood (or occasionally in adulthood) in which you were harmed, frightened, or rejected in some way, or in which you didn't get important needs met. The result is unresolved pain or trauma. For example, the Domination Wound leads you to expect to be dominated or to be afraid of being dominated. It is caused by being controlled too much as a child.
If you know IFS, a wound is a type of burden carried by an exile. For example, if you have the Abandonment Wound, it means that you have an exile who was abandoned.
NB - if you start directly from the Dashboard with resolving a wound, please note there are no Restart Points available (unless you have already commenced a Pattern) because they don't take that long to complete.