Also called the "on-demand economy," "sharing economy" or "instant gratification economy," the gig economy refers to temporary jobs that normally would be full-time occupations. Uber is the poster child for the gig economy, and ambitious startups in the field like to call themselves the "Uber of X" (Uber of food delivery, Uber of private jets, etc.).
Gig has nothing to do with gigabits or bytes. The word was coined by jazz musicians a century ago to refer to a performance. Today, a gig is any kind of a temporary job, although it may refer to a permanent one.
Freelancing, Sharing, Apps and the Internet
Freelancers (part-time drivers, landlords, etc.), and shared facilities (cars, lodging, etc.) make up the gig economy. The Internet and smartphone apps have been the catalyst, allowing people to sign up for services at any time and any place. See Uber