Technical question on how some of the equipment works

This isnt an encounter so I hope this still is permittable.

So I watch paranormal shows and occasionally Ghost shows and they have equipment that will show a "spirit" but it shows up like a bunch of dancing lines and dots (idk what its called so i cant look this up)

--my question is what is the technology actually picking up on or what is it triggered to pick up on? Most of the time these lines and dots are in the shape of people, is that how the technology is designed to make it look or is there supposedly something in that shape there? What level of accuracy does it have because these shows bust them out and there's always something there. I'm wondering if I bought one if id see a bunch of stick men in my house too.

Could these lines/dots be explained by a lot of other things? (Again dont know what this tech is measuring) If anyone owns this camera thing, id be curious to hear your opinions on it.

Thanks!