Made from a variety of different materials including wood, ceramic and metal. The earlier form was known in Europe as a Gemshorn. Unlike this instrument or a recorder, sound is created by resonance of the entire cavity. The placement of the holes is therefore largely irrelevant. 

It became popular in Medieval European communities as a toy instrument as it was cheap and easy to make.

Family of Instruments: The Ocarina belongs to the family of Woodwind instruments.

Medieval Musical Instruments - Ocarina
Medieval Musical instruments, including the Ocarina, would be used by the musicians of the period including the Waits, Minstrels or Troubadours. There were three categories of musical instruments in the Middle Ages - wind, string and percussion. Terms of description were Bas instruments and Haut instruments. Bas referred to soft instruments (literally, "low," but referring to volume, not pitch) which were suitable for the chamber which included the vielle, rebec and other bowed strings, the lute and other plucked strings. Haut referred to loud instruments (literally "high" but referring to volume, not to pitch) which were suitable for outdoors which included the shawm, sackbut, pipe and tabor.