Rami Arieli: "The Laser Adventure" Chapter 9.3.2 page 1
9.3.2 Laser Target Designator

The laser is used to mark targets for attack by "smart" artillery and guided missiles.

The properties that make the laser so attractive as laser designator are:

A soldier in the field, or a flying vehicle can be used to send a laser beam on the target.
The laser is designed to send a series of pulses in a specific pattern (code) of pulses of invisible light.
Special detecting systems are locked on these specific pattern of laser pulses, and guide the "Smart Bombs" to hit the marked target.
An example showing several laser designator system are shown in figure 9.1.
Figure 9.1: Laser Designator systems in the Battlefield.