This lesson focuses on understanding the concept of equivalence in mathematics, particularly using base-ten models. It begins by defining what it means for two values to be equivalent and provides an example with money, explaining that different representations can hold the same value. Students are encouraged to sketch models demonstrating equivalence, engage in discussions about this concept, and explore scenarios to test their understanding. The lesson culminates with a challenge where students create their own equivalent models for values between 10 and 100, reinforcing their grasp of equivalency in a practical context.