I'm new to python and programming in general but I'm looking into off site backup programs. I'm wondering how to code differential backups, any help would be greatly appreciated.

Now one will will code differential backups for you,and that is no point either
Because you learn little from it.

Start by moving and copying some files/folders around,like backup soultion most do.
Look into os module and shutil module
Some examples.

import shutil

#Copy a file from test folder temp folder
#shutil.move dos what name says
shutil.copy('c:\\test\my_file.txt', 'c:\\temp')

import shutil

#Will copy content in folder test and make a new folder temp that have the same content
shutil.copytree('c:\\test', 'c:\\temp')