It represents a particular touch point in your product or in your user journey, where it makes sense to display a paywall. Placements are hardcoded in your app in the sense that, this is the app that chooses which Placement matches where the users are in their journey.
For example, you can choose to use a different Placement at the app launch, after your onboarding, or for subscribers that you want to upsell.
You can remotely reconfigure in the console which paywall should be displayed.
You can also choose a paywall variant to perform an A/B test for a particular Placement.
Using different Placements will allow you to target users with contextualized paywalls.
For the sake of simplicity, you can start by putting the same paywall on all your Placements, and reconfigure them afterwards when you create or want to test new paywalls.
We recommend around 5-10 Placements are fair enough to have a run A/B test.
Refer to this article on how to create a Placement in the Purchasely Console.