DPICM is milspeak
unition. Typically, this term is used to refer to a particular type of submunition
which is loaded into artillery shell
s, bombardment rockets
, and air-dropped or air-launched
weapons, but can also apply to small-arms explosive ammunition.
The munition itself is really just a modified grenade. The 'dual-purpose' indicates that it is effective against vehicles/small structures as well as personnel. The general composition of a DPICM bomblet (the more official term for a singular unit) consists of a fuse, a casing, an explosive core (usually a shaped charge) and shrapnel (usually ball bearings).
The bomblet is weighted so as to fall with a particular side down. That side contains the 'mouth' of a shaped charge of high explosive with a copper or other light metal sheath on the inside of the 'cone.' Around the top of the weapon is packed a quantity of steel shot; all of this is held together by the case.
When the bomblet hits something (the ground, in most cases, but if you're lucky a vehicle or structure) the shaped charge in the core detonates. This causes a self-forging warhead to fire down the 'mouth' of the shaped charge - in other words, down into whatever it has landed on. Since shaped charges aren't perfectly directed, the explosion also throws a ring of high-velocity shot outward.
The main charge is intended to disable or destroy larger targets by causing a small number of high-powered penetrations. The spray of shot will kill humans, as well as shred unarmored vehicles (say, trucks) that happen to be nearby. The shaped charge is what makes this an 'Improved Conventional Munition.' It allows a fixed quantity of HE to become much more effective against certain targets.
The advantage of these is that they are small and cheap, and can be packed into delivery systems such as MLRS, ATACMS, cluster bombs, etc. etc. by the dozens and hundreds. Coupled with some design resources on the method of scattering the submunitions, a single delivery vehicle has a very good chance of at least damaging anything (person, place or thing) within a much larger area than would be at risk from a blast from a unitary warheadof the same size.
There are, of course, disadvantages. The bomblets aren't very effective against larger structures or heavily armored vehicles. Their narrow and deep penetration means they won't significantly harm reasonably well-constructed bunkers. There is also a small delay between the dispersal charge and the submunition detonations, meaning a very alert soldier might be able to take cover. Finally, a certain number of the bomblets fail to detonate on impact, making the area extremely hazardous to enter until mineclearing routines have been undertaken. The U.S. tends to use self-destructing bomblets which neutralize themselves within a few hours, but these are naturally more expensive.
If you ever find yourself needing to shoot at infantry and trucks (and even light armored vehicles) and you're not exactly sure where they are, call in a battery-three of these puppies. That should do you just fine.