Most use three matzot at the Seder while some use two. Maimonides writes that we use two, break one of them, and then recite the blessing over a whole piece and a broken piece. This demonstrates that matza is bread of the poor. Why use three matzot? Three matzot accompanied the korban toda – the thanksgiving offering – that was brought to the Temple. R. Isaac of Vienna (d. 1270) explained that leaving Egypt is worthy of a thanksgiving offering and that's why we use three matzot at the Seder. At the heart of this dispute is whether to emphasize our affliction or our freedom. The dominant practice to use three matzot reminds us to focus on the positive.