A Look-alike audience is an audience that is similar in some ways to the original one.
Let me explain with an example. Let’s say you need to receive orders. You upload to the advertising account information about those users who have already made an order with you. The social media algorithm finds out what your customers have in common (place of residence, interests, behavior on the Internet), and makes a selection of users who have not ordered anything from you yet but are similar in some characteristics to your customers.
There is an algorithm that can collect similar audiences on Facebook and Instagram.
Practice shows that Facebook defines look-alike audiences quite accurately. That is, users collected using look-alike respond well to targeted ads.
However, it’s important to choose the right target audience for your look-alike ads to be effective as well.