Customer Chat is a plugin from Facebook, which allows you to integrate your Messenger experience directly into your website, making it essentially a Live Chat plugin.
This plugin provides the easiest way to integrate the Customer Chat feature to your NopCommerce site. It only requires that you enter your Facebook Page Id to the configuration page of the plugin.
You can find your Page Id, in the About section of your Facebook Page.
It is recommended to whitelist the domain of your website in Facebook by doing the following, while logged in to Facebook:
More information about the "Customer Chat Plugin" of Facebook can be found here