Explanation
App page and record page are two types of pages that an administrator can build and customize using Lightning App Builder for Salesforce mobile app. App pages are pages that display informationor tools that don't belong to a specific record; they can be accessed from navigation menus or tabs in Salesforce mobile app. Record pages are pages that display information or actions related to a specific record; they can be accessed by opening any record in Salesforce mobile app. User page and dashboard page are not types of pages that can be built using Lightning App Builder for Salesforce mobile app; they are types of pages that can be built using other tools such as Profile settings or Dashboard Builder.
References:https://help.salesforce.com/s/articleView?id=sf.app_builder_mobile_pages.htm&type=5