Counter-Strike is a modification1 for HalfLife, a 'First Person Shooter' game made by Valve Software.
There are several different scenarios in Counter-Strike, from Hostage Rescue to Bomb Disposal through to Assassination. All scenarios are based around two teams broken into separate factions. Terrorist and Counter-Terrorist, each of which has several different skins2 and different goals.
Counter-Strike features a deadly array of hyper-realistic weaponry, from the Glock 18 Select Fire Pistol to the Para M249 Machine gun, and everything in between (Submachine Guns, Rifles and Shotguns). It is this stunning realism, along with the creative maps that the people play in, that have made Counter-Strike an instant worldwide hit.
What makes Counter-Strike different to other games is the need for self-preservation. When you are killed in Counter-Strike, you will not respawn3. Other games like the Quake series and Unreal Tournament give you infinite lives, in Counter-Strike once killed you will float around as a 'ghost', where you are invisible and unable to affect the world.
In order to succeed in Counter-Strike, you'll either need a team of computer legends capable of seeing the future, or some serious team strategy. Each weapon in Counter-Strike is individual and has different handling abilities, and so each member must choose their favourite weapon, or the best from what they can afford4.
For example, the Para Machine Gun is rarely useful in open areas, and even in confined space is not accurate enough to cause adequate damage to your enemy, it is however good for suppressive fire. Forcing the enemy to run away will give your Assault team - usually three or four players - a chance to achieve their mission objective.