Google is being a bit difficult since apparently a million and a half people have footprint written somewhere in their resume. Who knew?
The only description of one I could find was: a brief summary of your experience, special talents, and skills
I'm not exactly sure how long it's supposed to be, how it's supposed to be written or anything or even what's supposed to be in there (if there's a skills section in your resume, what skills would you put in the footprint? How are you supposed to word your experience if you already list school and work experience?) so that's why I'm asking.