An 'Input' is anything submitted to your 'Crowd'.
In process terms, an input is the start of the process and completing that process transforms the input into an output. For more on this read: What is a Process? And who Cares Anyway?
In the ATC platform, inputs are also the start of - or the trigger for - the process. Inputs can be submitted to your Crowd by both your Users and anyone who has made an external submission. (This just means an input submitted by a non-user.)
With change management your inputs will be change or improvement ideas, for submission to your change roadmap.
In both cases the Moderator should review the input and allocate it to the correct Topic and Process Owner.
In the List View inputs are summarised as Input Slates.
The full input view is called the Input Detail screen.