Traps does a static amount of damage. 30 to be exact, it's always 30.
However, traps cause a physical damage that listen to the creatures armor.
It means that the damage can and will be reduced by any armor the creature may have.

As seen here, a weak Troll takes a lot more damage than a strong Hero.
And if the damaged creature would happen to have an armor boosting item equipped, it would done even less damage!

You cannot move open traps, they will close instantly if moved!
That means you can't just open them in your inventory and throw in front of your target!

You cannot put items on the trap either, it will close at the slightest breeze!

Traps cannot hurt players!
As of Tibia's update 7.2, traps could no longer inflict damage towards players!