' { } ' symbol in as3

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Flash

AS3

hello. I am a bit confuse about the symbol of ' { } '

can someone please explain to me how to use this symbol
and what does it means?

example :

var tween = TweenLite.to(demo, 20, {score:100, onUpdate:showScore})

what does {score:100, onUpdate:showScore} means?

and how it works?

thank you..