This is a variation on the classic push down and watch it spin type toy.
It has 2 layers of bright balls which are either made to look like red/white ladybirds or blue/green butterflys. When the top plunger is pressed down the little balls whirl round the central mirrored column and make a fascinating noise and sight.
Downsides are: The name is misleading, as it's not very rainbowy, it would perhaps have been better called a pixie spinner. At the