They can exist as entities by themselves, at least for a while. They are basically inanimate, non-thinking forces. Talking to one is about as logical as talking to a chair. In this way, thoughtforms are similar to elementals, ghosts, and spirits. All of these psychic entities consist of a psychic energy vortex which could be described as a localized field or as a discontinuity of the physical world.
Psychic entities respond to certain electrostatic and magnetic fields, and to other energy vortexes.
That is why they respond to magick ritual. Someday, we may accomplish the same thing with electronic machines. Psychic entities are sometimes able to affect our thought processes. Thoughtforms, elementals, and ghosts are usually not very smart. If they display any intelligence at all, it is limited.