In a red dot sight, the dot is not projected on to the target, it is only seen inside the sight and only by the shooter. Lasers project the reticule on to the target which makes the dot visible on the target. The red dot sight uses a LED (light emitting diode) which is completely safe for the eyes comparted to a laser that create a reticle with a laser emission, which can be harmful to your eyes.
Aimpoint® series sights feature either a 4 MOA dot or a 2 MOA dot.
MOA stands for "minutes of angle" and 1 MOA = 1"at 100 yards = 3 cm at 100 meters
If you have a 4 MOA, this means that the dot is about 12 cm at 100 m (4" at 100 yards), 6 cm at 50 m and 3 cm at 25m.
If you have a 2 MOA dot, this means that the dot is about 6 cm at 100m (2" at 100 yards), 3 cm at 50m and 1.5 cm at 25m