Core Audiences: Audiences are based: age, interests, geography and demographics etc, These are the information which already shared by the users in their profile. With Core Audiences, you set the rules for where your ads are delivered. Adjust your target audience to be as broad or well-defined as you like, based on the following criteria.
Custom Audiences: lets you find your existing audiences among people who are on Facebook. You can use sources such as customer lists, website or app traffic, or engagement on Facebook, to create Custom Audiences of people who already know your business. Custom Audiences allow you to connect with people who have already shown interest in your business, whether they’re loyal customers or people who have used your app or visited your website.
Lookalike Audiences: Reach new people whose interests are similar to those of your existing best customers. Lookalike Audiences are a fast and effective way to connect with people who are likely to respond to your ads. All you need to do is create a source audience of people you know. Your ads will then reach people with common interests and traits.