Teaching Portfolios are a way to document your effectiveness as a teacher. Below are some resources that will give you a better idea of what a teaching portfolio is, why it is important and how to create an effective portfolio.
Designing a Teaching Portfolio - Schreyer Institute for Teaching and Excellence, Penn State University
Creating Teaching Portfolios: A How-To Guide - Penn State University Libraries
"What is a Teaching Portfolio" - University of Saskatchewan
More links to teaching portfolio resources - Compiled by the University of Medicine and Dentistry of New Jersey.