Asymmetrical warfare involves fighting between nations or quasi-states,in which one side does not directly confront the strength of the other. The term came into use as the "war of the weak", applied to guerilla warfare and terrorism against traditional militaries, but is also used for high technology against a more conventional force.
There was considerable asymmetry in the 1991 Gulf War, with a relatively long air campaign, Operation DESERT STORM, followed by a short ground campaign, Operation DESERT SABRE. Iraqi air forces had very limited relative capability vis-a-vis the coalition, but their ground forces were strong. One of the goals of the air campaign, to which the Iraqis had little effective countermeasures, was to attrit the ground force and its logistical support. The current no-fly zone operations in Libya used specialized techniques to destroy the Libyan Air Force and to keep it from allowing Libyan government forces having one major asymmetrical advantage against the rebels.
Part of broader strategy
It may be part of a larger grand strategy, as, for example, Soviet partisans harassed the German rear areas during Operation Barbarossa. United States Army Special Forces were created to organize guerilla warfare by the people of occupied countries, after an expected Soviet invasion.
Weapons of mass destruction
Warfare between a state with nuclear weapons and one without them, especially when the nuclear state has not pledged "no first use", is asymmetrical.
Operations against command, control, communications and intelligence often require specialized information operations and electronic warfare. Destroying deeply buried command centers, as well as WMD facilities, may need hard target penetrators or other specialized attacks.
Nonviolent national war
Asymmetric warface does not always involve direct military confrontation. Economic warfare and lawfare can be effective asymmetrical threats, as can be well-considered propaganda.
Relatively nonviolent revolution
In a current context, asymmetrical warfare can also include managing rapid protest against a government not willing to use massive force against demonstrations. It has taken place in the Philippines using texting to organize protests against a corrupt government, and widely during the Arab Spring using social media. Egypt attempted to shut down many personal communications services and social media, but some still operated and had an effect.