Indoor kites are kites designed to fly in a windless environment. Often they are called "zero wind" kites. Whilst principally designed for indoor use, they can also be flown outdoors when insufficient wind would render conventional kite-flying impossible. They are flown by using the relative wind provided by the motion of the kite-flier. This motion is typically generated by the user walking slowly backwards (and often within a circle), but it can also be achieved with suitable pulls and jerks along the kite lines.
Indoor kites were developed from low-wind kites, as ultralight modern kitemaking materials became available. Usually Indoor kites are single-line, dual-line SUL (super ultra light) Stunt kites and quad-line kites. The dual-line indoor stunt kites are capable of performing most of the same tricks and maneuvers as an outdoor sports kite using short, thinner lines (~5m length). Maneuvers which require mass are quite difficult, due to the lack of such in indoor kites. They may also be employed as decorations or artworks, where they waft upon air-currents.
The good thing about indoor kite flying is that you don't need to check the weather forecast before a session or kite festival/event. Just go and have fun. Some of the maneuvers and tricks in stunt kiting are easier to learn in low-wind conditions or indoor because the kite flies slower. Feel the tiny changes in line tension directly through your fingers!