Sections have two options for display on the mobile devices: Drill Down and Inline. The difference between the two is how the section is displayed on the mobile device.
Drill down display will make the sections show up on its own page. This option breaks up large forms into smaller pieces and makes it easier to navigate on the device. It can also help reduce the memory usage of the device. It adds some navigational hierarchy so that the app does not have to load all of the fields inline. Ultimately, this is a great option for bulky apps that need to load faster. Using the drill down display permits more memory allocation for multiple fields.