http://www.nytimes.com/2010/01/24/world/asia/24trap.html
“…Homemade bombs, which the military calls improvised explosive devices, or I.E.D.’s, have become the insurgents’ killing tool of choice in the Afghan war, a complement to the Taliban’s assault rifles, machine guns, mortars and rocket-propelled grenades. They serve as a battlefield leveler for elusive fighters who are wary of meeting Western forces head-on.
As their use has multiplied several-fold in the past two years, bomb-disposal specialists and American officers say, the Taliban’s bomb-making cells have sharpened their skills, moving away from smaller bombs in cooking pots to larger bombs encased in multigallon plastic water jugs, cooking-oil containers or ice coolers.
The bombs typically contain a slurry of fertilizer mixed with aluminum-based paint, and are triggered either via switches tripped by their victims or by a militant who detonates the weapon remotely when a victim moves near. Sometimes the insurgents use military-grade explosives from unexploded ordnance or conventional land mines.
…An improvised bomb is a simple thing — a few batteries, a few wires, a blasting cap or two inserted into a stable explosive charge. A pressure plate serves as a switch. When depressed, the circuit is closed, the current from the batteries flows to the blasting cap, igniting the cap and setting off the full blast.
Ordnance specialists have a label for devices designed this way: victim-operated. "