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Battery has 3 wires??!!!

Hi,

Sorry if I'm being naive but I just got a lithium -Ion rechargeable battery pack (8.4V 2000mAh(2C)) and guess what..Yeah it has got 3 wires (a red one,a yellowish creamy one and a black one).Now could u please tell me what each one means and also the need for doing this.Btw what does 2C mean ?

Thanks in advance.

charge91