Thing Rattling Between Brake and Front Wheel

I have a 2000 Toyota Sienna. The font wheel has been squealing so I took it off and found this between the wheel and brake. What is this? What was this for? Thanks!

 

It's called a brake dust shield. It also serves to direct air thru the brakes for cooling.
It sits behind the rotor and bolts on to the back of the brake caliper bracket.

 

Does this car have brake shoes or disc brakes?

That's some small pieces by looking at the crack in the concrete & the leaf on the ground. It looks like the little nickel size keeper that goes on the the end of the spring between the top & bottom of the brake shoes. That think should be completely round with a little slotted hole in the center.
The long rod looks like the long spring that pulls the brake shoes back to a resting position when the brakes are released, although I've never seen the crook in the end look quite like that, but I am not familiar with every car's brake spring design.

 

OK thanks for the replies. How critical is it that I have this shield replaced? What's involved installing one? Because I'm wondering if I can do the job myself. I have reasonable mechanical ability, but not crazy about working on autos.

 

I have no idea what that black hook piece is.
Doubtful it belongs on that brakes.
The shield should be replaced.

I believe you'll need to remove the rotor to replace that shield.
Here's a good video on the repair..... replacing dust shield.

You'll need more detailed vehicle info to locate part..... just an example