A source audience is the audience a Lookalike Audience is based on. For example, if you create a Lookalike Audience from your Page fans, your Page fans would be the source audience.
About Brian Meert
Brian Meert is the CEO of AdvertiseMint, a Hollywood-based digital advertising agency that specializes in helping successful companies advertise on Facebook. He began his online advertising career with his college cafeteria money and since then, has managed millions of dollars in digital ad spends in the entertainment, fashion, finance, and software industries. Brian has an MBA in marketing and over 15 years of experience in digital marketing & advertising.