How to use Code?

I saw in some topic and saw Code, what is it? how can I use it? example: 9FXR-UZ6A-V7WG-HLTA.

this code is redeem code , u writte it here : http://www.battlefieldheroes.com/en/store/redeem
this code can give you gifts like : 1 day weapons 3 days weapons , etc... =) thank me if i helped you