Assault is when one person does something that causes another person to believe that he or she may experience immediate physical harm or unwanted bodily contact. Assaults can be either criminal or civil. Clear intent, and the capability to cause harm or make the unwanted contact, are both neccessary to constitute assault.
Assault is often accompanied by battery. This happens when one party follows the assault with a physical attack on another person. An example of assault would be if one person threatens to hit another person with a baseball bat and then goes and gets a baseball bat out of his/her car and starts waving it at the other person. If an assault charge is accompanied by battery, then the punishment can be much more severe and lengthy.