If you want to make it so that your app only displays a particular subset of your data, you can create a data filter.
For example, let's take the app we've previously been working on, which allows you to browse vacation spots. Suppose you input all of your data into a Trips Collection with many Properties, one of which is a True/False criteria describing whether or not the trip is public. Let's say for your app, you only want to display trips that are public. You also want to sort the trips from low cost to high cost.
Insert a list
Select what database collection your list is of
Click 'Add another filter' to insert a custom filter
Select which Property you want the filter to depend on (in this case, Public)
Choose the condition of the Property that you want to filter for (True/False, Between, Includes, Excludes, etc)
Under Sorting select how you want to sort your list (in this example, Cost- Low to High)
After filtering, only the trips that had been tagged as public showed up in the preview.