So what are sirens and how do they look like? They are tall lanky creatures, half humans half robots, with wires running up their legs and hands. Instead of heads, they have speakers producing awful sounds. These sounds can shock you and sirens will finish you off as you lie unconscious. So you have to be very careful, move quietly and avoid attracting their attention.
In most of the games, you will have a gun that you can use to protect yourself. Aim for the head if you want to put a siren down for good. Just remember than gunshots can attract other sirens and it won't be so easy to get rid of them, so you only have to resort to fire when you have no other choice.
Some of the games will also include elements of puzzles. You'll have to find a road leading out of the forest, or enter a security code at an abandoned military base, or search for some objects necessary to get out of the locations. In any case, stay on your guard and don't let sirens get close to you. The atmosphere of dread and suspense will be hanging over you every minute of the gameplay. Prepare for a lot of challenge and scary situations! See if you can survive!