Inbox will show you all features in the feature service connected to that survey (but can be filtered by putting a "where" statement on the Inbox in Survey123 Connect). An example of this would be something like a "work orders" survey that filters its inbox to show "open" requests based on a status field.
A sent box, on the other hand, is specific to previously-sent forms from that particular device. Nothing will appear here until the form is used at least once.
To your question: what's the difference between the two when it comes to sending / uploading data? Nothing! They are simply ways of seeing and editing existing entries; while they show different lists of data, they are part of the same form.
- Josh Carlson
Kendall County GIS
