x is the horizontal position of a object, defined in pixels. Left is 0.
To return any objects X or Y position, you can use this code:
obj_wood.x to get the X position of the object wood,
obj_wood.y to get the Y position of the object wood.
Example: instance_create(obj_wood.x,obj_wood.y,obj_woodlover)
This code will summon obj_woodlover on the X and Y positions of obj_wood.