They are basically created “spirits” – you created them out of your own energy, give them a form to exist as – and give them a set task/purpose, to do while they exist. For example, say you want an aid in protection for during a particular ritual or holiday, you could create a thoughtform for this purpose, and destroy it once the ritual or holiday is over.
think of it sort of like making an energy roomba.
it helps you with your spiritual “chores/tasks”
and when you don’t need it anymore, you get rid of it
If that helps make any sense?