Personal content extensions allow for a user's session to be carried across from the app to content served by Sales Force Commerce Cloud within the app. This means that you can serve user content to users that would normally require the user to be logged in. For example you could display a more detailed "My account" section where the user can fill in some personal details, or a page that users can use to track their latest orders.
Personal content extensions are supported on the account view of the app. The user is required to be logged in. A url to a page served on the SFCC domain will need to be configured in the app. Upon clicking this url the app will then make a request to the POST /sessions endpoint on the OCAPI. This endpoint will return a set of cookies that are then added as headers when requesting the personal content extension url. SFCC will then use the value of these cookies to keep the user logged in on the web page.