Explosive

 ammunition is, obviously, the type of ammunition that explode upon impact, transforming chemical potential energy into explosive kinetic energy.

Fallout, Fallout 2
In Fallout and Fallout 2, the only types of explosive ammunition are the Explosive Rocket and the Rocket AP.

Fallout Tactics
Fallout Tactics has several more kinds of explosive ammo types, including Explosive Rockets, Rocket APs, Rocket Sabots, and 40mm grenades

Fallout 3
Explosives are almost always more powerful the closer a target is to the center of its blast radius in Fallout 3. This blast radius is known as the Area of Effect, or AOE.

Examples of explosive ammunition are the Missiles that are used by the Missile Launcher and derivatives, and the Mini Nuke shell for the Fat Man catapult.