Eye pins have the same basic function as head pins, but instead of a horizontal piece on the end of the pin there is a loop. This is helpful when you want to add an extra dangle, e.g. to the end of an earring.
You can also make your own eye pins with the appropriate pliers like wire-looping pliers or even the roundnose/rosary pliers.
Both the head pins & eye pins are basic essential findings for jewelry making. They are used in many bead style earrings or for attaching beads to any type of jewelry piece. If you are into jewelry-making, you can't do without these!