lookalike audience !!!!!!!?

hello

please can someone explain to me what is mean lookalike
and how does it work ?

Thanks a ton

Hi!

Facebook Lookalike Audience is an advanced targeting option for segmentation of users similar to you established customers. Lookalike audiences take several sets of users and then Facebook builds an audience of similar people. You can use lookalikes for any business objective: Targeting people similar your customers for fan acquisition, site registration, off-Facebook purchases, coupon claims, driving awareness etc.

You can read about it more on Facebook, here