A NAP or Non-Aggression Pact is an agreement between players or alliances not to attack each other. It is less tight than a confederation pact or alliance wings.
NAPs tend to divide into two categories, the "friendly NAP", where alliances could move toward a stronger pact (or when players agree to peace), or the "hostile NAP", between alliances that could inflict serious damage on each other with no real winners.
NAPs are not recognized under friendly fire rules, so violating a NAP is not friendly fire.