This booklet provides an overview of the principal concepts of pension portability. Pension portability has become an area of increasing interest since a lack of portability discourages veteran teachers from seeking teaching opportunities in other districts or states. This obstacle can force teachers to abandon the profession, thus contributing to the increasing shortage of qualified teachers. The text examines the major types of pension plans, the current status of plans covering K-12 educators, and recent state actions to improve pension portability for teaching professionals. It also includes steps designed to help state policymakers ensure a fair and open process for modernizing retirement systems for a changing teacher work force. Some of the areas that the document focuses on are the structure of defined-benefit plans and defined-contribution plans and the advantages and disadvantages of such plans. It also examines the status of pension plans covering K-12 teachers and claims that by shortening defined-benefit vesting periods, by simplifying defined-benefit service-credit purchases, by instituting interstate or intrastate reciprocity agreements, and by adopting defined-contribution plans, state legislators can improve pension portability. Legislators also must identify clear state goals, keep changes targeted to specific issues, and allow adequate time for implementation. (Contains glossary and 16 endnotes.) (RJM)