Identify a round kitchen tool with perforated and hinged metal leaves

It's a steamer basket.

If you pull the leaves apart it will look like this:

Then you put it into a saucepan like this:

You put water into the saucepan (the legs at the bottom keep the bottom of the basket clear of the water). Then you can use it for steaming vegetables, dumplings, etc. You put a lid onto the saucepan to keep the steam in.

That is a steamer basket. Put an inch or so of water in a pot and drop that in (other way up). Add some veggies (or other food), and cook until done.

It does look like a steamer basket as the other answers mentioned.

If the need comes to take it out from the pan/pot after the water is boiling, I'd personally suggest to use a tool with a hook, e.g. a soup ladle:

1. connect the hook to the center ring of the steamer basket;
2. lift it off a few centimeters over the water;
3. let it drain for a few seconds before attempting to move its contents to a new recipient/container (or taking it out completely).

If the steamer has no ring to attach the hook to, you may use the soup ladle and a spoon to scoop out its contents (to prevent overcooking), avoiding to push down the basket petals.

A couple of other possible usages:

• rinse light food with water (similarly to a light strainer) if placed in a large pan/container as Nick depicted (the rinsing water can be saved for other purposes, e.g. for watering plants);
• cook large pasta (e.g. fusilli or conchiglie) with it, i.e. similarly to a pasta cooker: