Friendship doesn’t let to attack a player from the friend list. It gives ability to organize joint attacks using CAS and defend friend's objects.
Non-aggression pact means impossibility to attack any player from alliance with which NAP was accepted. Territorial tribute is not charged from members of alliances, which signed a nonaggression pact.
Collective Security Agreement allows all members of your alliance to send a fleet to defend planets, asteroids or moons of alliance members contracted. During the joint defense of coordinates, without signing of Non-aggression pact, fleets from alliances which have signed Collective Security Agreement will start to fight.