Beading a target is the act of taking aim. The longer you take aim before you fire, the better your shot will be. You will know when you have a full bead on a target when the 3 arrows on the edge of your reticle stop moving in. Each weapon gets a bonus with a full bead such as increased accuracy. Another way to increase accuracy when firing is by taking a knee or sighting down the barrel of the weapon (done by pressing the 'g' key on the keyboard.