What is the Poppet?

When Mary Warren returns from her day in court in Act II, she gives a poppet, or small doll, to Elizabeth Proctor, saying, "I made a gift for you today, Goody Proctor. I had to sit long hours in a chair, and passed the time with sewing" (Act II, p. 56). This poppet is later used as evidence against Elizabeth Proctor when Marshal Herrick reveals a needle inside the doll. Abigail Williams, that evening, collapsed with pains in her stomach, revealing a needle, which she claims was placed there by the familiar spirit of Elizabeth Proctor.