Fraction strips are rectangular pieces (electronic or copied on paper strips) to represent different parts of the same whole. Using fraction strips, you can identify equivalent fractions if they take up the same part of same size wholes.
Fraction strips can be cut apart and manipulated to see how various parts can be added together to make the whole or compare different fractional amounts for equivalency. See sample activities here.
Of interest, math is getting a major makeover. By fall, traditional textbooks mostly will be tossed aside in California classrooms. What's taught in each grade will get shuffled around and, often, merged. First-graders will get tiny tastes of algebra while learning to add, and middle school students will be exposed to statistics and geometry while still solving for X. Find out more at SFGate.