A Gig Owner is the person who needs help getting a job done, while the Helper is the person who carries out the work for them. Say, for example, you get somebody to work in your restaurant for a night as a waiter. In this example, you, the restaurant owner, are the Gig Owner, while the waiter is the Gig Helper.
As another, connected example, say that this waiter (from above) got somebody through Gigable to walk his dogs while he was at work, he would then be the Gig Owner for the dog-walking Gig and the person walking his dogs would be the Gig Helper on this Gig.
Users have the freedom to be either Gig Owners or Gig Helpers as they so choose.