the goal of the game is to reach a certain point in the level (the exfiltration point). Opposing you are the opposing forces. They are armed and will do what they can to prevent you from advancing, chiefly by killing you. To prevent that, you must survive enemy gunfire by neutralizing them before they kill you
Neutralizing Hostile Threats
You have a wide variety of weapons to pick and choose from; take what you want, and leave the rest (just like Kim Catrall's salad bar in Big Trouble in Little China). Some weapons come attached with multiple attachments (generally the optimal weapon for story mode) while others come with a single attachment.
In story mode, only the weapons you start with have multiple attachments; enemy weapons have no attachments or single attachments.
Story Mode Attachment - IR / Infrared
A special scope is attached to this weapon which highlights organic objects, chiefly human beings. Note that in real life, IR doesn't work in desert terrain until the temperature has dropped off (typically two hours or more after sunset) as humans will be camouflaged by the hot ground.
When this attachment is available, it is generally for night-time missions with poor normal visibility. Use FLIR to actively locate and identify threats you otherwise couldn't see in the first place
Story Mode Attachment - ACOG
Advanced combat optical gear. Generally applied to rifle sights and scopes built for rugged battlefield use. The ACOG in the game gives you a slightly enlarged view of the targeted spot, allowing you to snipe enemies from longer than normal ranges. Unless you're in a rush to finish the game (or there's a G—D— time limit), you should stick with an ACOG weapon and shoot enemies from afar.
Lethals vs. Non-lethals
Your operator has access to lethal devices and LTL (less than lethal) devices. For hostage-sensitive situations, LTLDs are used to incapacitate all targets without injury, allowing the team to sort out the friendlies from unfriendlies (some counter-terror units never learn this and are piss poor examples of true CT practitioners).
Lethal devices will kill everything in range (especially on veteran) and are used when enemy concentrations are proof-positive present (and engagement is authorized). You can throw either type of device instantly with the shoulder buttons, giving you a quick way to respond to developing situations.
About this game
Hear the call of duty once again with this seventh entry in this blockbuster first-person shooter franchise. Call of Duty: Black Ops takes you deep behind enemy lines into the world of deniable operations as a member of an elite special forces unit engaging in covert warfare, classified operations, and explosive conflicts across the globe. With access to a variety of exclusive weaponry and equipment, your actions will tip the balance during the most dangerous time period mankind has ever known.