"Symbol of a meeting"
When Link first meets up with the jeweler Vasu in Horon Village or Lynna Village, he is given the Ring Box along with a Seed Ring. Vasu then offers to appraise the ring at no cost. This first ring is always the Friendship Ring.
When equipped, the Friendship Ring has no effect at all. The purpose of this ring is simply to introduce the ring system to Link, along the with process of appraising and wearing rings.