If you are referring to pre-astral projection vibrations it is the simultaneous perception of the movement of a different configuration of matter against another.
Basically you are feeling the vibration of astral matter against the physical matter. A sort of "collision" is taking place because you are picking up sensations from two planes of being at once. Vibration is just how the consciousness intreprets this impression.
Basically you are feeling the vibration of astral matter against the physical matter. A sort of "collision" is taking place because you are picking up sensations from two planes of being at once. Vibration is just how the consciousness intreprets this impression.