Chemical light is nothing else but fluorescent tubes which start glowing after they get broken. They more or less behave like road flares, though they give much less light and are used mostly for tactical actions. A raised chemical light is perfect for team play, as players can easily notice it even during the darkest night. It comes in three colours: blue (giving the most light), green and red (the weakest and least visible from afar). After throwing away, chemical light can be picked up and extinguished just like road flares. It also floats on water.
Chemical light cannot be taken into vehicles (even a bike), but they appear back in your hand after you get out. Sometimes you might be able to "stick" a glowing stick by throwing it at the vehicle. Both effects are caused rather by bugs than intentional.