It's a conjuration with a duration other than instantaneous.
"Creation: If the spell has a duration other than instantaneous, magic holds the creation together, and when the spell ends, the conjured creature or object vanishes without a trace."
As Thanee says, only Instantaneous Creations (like the Orb spells, or Acid Splash) will work in the field: "If the spell has an instantaneous duration, the created object or creature is merely assembled through magic. It lasts indefinitely and does not depend on magic for its existence."