Like in real life, flashlights are used to light up darkness in the direction that Albert West is facing. Using a flashlight requires a charged power pack to be equipped, and it will slowly consume power while it is used, albeit it is an almost negligible amount. Flashlights can be researched at the Tech Research System and then produced at the 3D Printing System.
Light sticks differ from actual flashlights in many ways, with the only real similarity being that they are used to light up areas. Light sticks do not consume power, and thus do not require an equipped power pack. They cannot be produced nor researched, only found around randomly, usually in security offices. They only produce light in a small area around West, rather than directly ahead of him. Interestingly, they also stack, up to 99, and the entire stack can be equipped (although to no effect, other than saving an inventory slot).