What kind of *.pdiff files does apt download?

Question

linux

I update the list of packages with apt update
And I get something like this in response:

Get:50 http://ftp.us.debian.org jessie-backports/contrib i386 2016-10-14-0326.10.pdiff

What are these .pdiff files?

Answer 1

patch file - contains differences between two files to update the old file