It's an IDA Plugin to diff binaries. Very useful for creating 1-day exploits i.e. when a vendor patches a vulnerablity, you use Diaphora to diff the vulnerable

It's an IDA Plugin to diff binaries. Very useful for creating 1-day exploits i.e. when a vendor patches a vulnerablity, you use Diaphora to diff the vulnerable binary vs the patched one to understand what was going on, and create an exploit based off of that. Many of Microsoft POC exploits that come out after an update are made this way.