The Taken are villagers of Bright Falls who have been overcome by the living darkness that threatens the area. The Taken were once normal people, before being pulled into the darkness - literally "taken" - by the Dark Presence, and twisted into soulless monsters, mindless killers which appear out of nowhere to slaughter anything in their path - usually Alan Wake - with melee weapons and throwing knives. There is also a lesser form of being Taken, referred to as simply being "touched by the Dark", which allows people to keep their souls, rendering them possible to be saved, and giving the Dark Presence a limited ability to enact its will during the day. Touched people will be compelled to follow the instructions of the Dark Presence, and tend to give their state away by speaking in a monotone voice and appearing confused or controlled. There is at least one woman in Bright Falls that acknowledges the Taken and the Darkness' omnipresence, Cynthia Weaver, the lantern lady!
The Taken are clouded in living darkness that buffers them from all harm until it is burnt away by searing light sources, be they flashbang grenades, flashlights, or the occasional spotlight that happens to be lying around. You can technically burn off the darkness by aiming the regular flashlight beam at them so as to conserve batteries, but this takes an extended period of time, something that might not be an option if there are a lot of threats nearby. More powerful Taken are covered in more powerful Darkness, which resists ordinary light and even regenerates when the Taken steps back into the dark. These Taken are indicated by the circle indicator on their darkness being orange, in which case only focused light will burn it away. When the darkness shielding a Taken is gone, the taken show less fear to light sources, becoming blinded by it less often and can be killed by a sufficient number of bullets. Much to the relief of Jeff Gerstmann, headshots do not work any more effectively than shooting them anywhere else, and will only serve to present a smaller target. Aim for a shot to centre mass as it will also slow them temporarily.
The Taken speak constantly to alert the player to their continuing presence and their voice is circuit-bent and occasionally has double tones which is meant to disconcert the player also. The Taken are mindless, and the things they say tend to be topics important to the Humans they used to be, but presented entirely without context in a non-sequitur, extremely aggressive manner. This means that while the Taken are attempting to murder Alan with everything from mining tools to nightsticks to chainsaws, they babble at him about everything from the wonderful scenery, the best eateries in Bright Falls, and important safety announcements that Alan really should consider visiting; because the Famous Dog (known to some as the Famous Durger) is third best.
Taken move sporadically, fast and in a seemingly random pattern with the exception that their singular goal is to ferociously attack anyone who is not Taken. Often times the player will be flanked by enemies as one of their most popular tactics is to leave one Taken straight in the fray as another hangs back and throws projectiles (or whatever is to hand) at the player while a third or fourth slinks around and out of sight to get around the back or sides, aided by the cover of the bush, as they are often found in the forest.
Taken will show up either in predefined positions about the game map or in areas of the map which are not directly story related, where they will spawn indefinitely in groups of three or more to use their basic tactics against the player. You can instantly recognize infinity-spawning areas because the screen will become very foggy and windy very suddenly and the tense music will play. In these areas it is better to accomplish what you need and leave quickly rather than stand and fight, beware ammo is limited in this game, you don't have a melee attack of any description, and some of the Taken are faster than you, so run in zig-zags to avoid projectiles and dodge, don't sprint!
You can expect Taken to appear as villagers (loggers, hoodies, big boys) as well as birds (usually ravens, birds known in folklore to be made themselves from darkness) but more frighteningly, objects can be Taken, though the actual enemy type is referred to as "Poltergeists". Any random object can become a Poltergeist if possessed by the Dark Presence, ranging from discarded industrial supplies, rusting minecarts, broken appliances, and even heavy vehicles. The only help I can give for vehicles is kill them for the achievements as running don't make them pop!