Both Heimdall and Odin have options for a PIT file. From Heimdall's option you can find,
[--file <filename>] [--verbose] [--no-reboot] [--stdout-errors] [--usb-log-level <none/error/warning/debug>]
Description: Prints the contents of a PIT file in a human readable format. If a filename is not provided then Heimdall retrieves the PIT file from the connected device.
And, from Odin there is a specific tab for it, when you click on the tab it says,
Do not use this tab. This tab is for engineers. You device will be changed with the pit in the CSC file.
So what is a PIT file, and where is it documented anywhere? Can I generate one automatically?