These are used by real estate agents and brokers for example, to showcase a property and give the feel that you are there. There are endless possibilities on how one can built these. I have used software that creates applets, flash movies, and more. I have also built them from scratch as seen below. The demo below is a simple one that allows one to click through to view 360 degree views. You can stitch together images taken with any device and make these 360 degree panoramas. Some cameras and mobile phones have a 360 degree app. built in and panorama photos are super easy. Then you need someone to build the viewer, which is where I come in. The viewer can be made many different ways.
The viewer can customized, and there are multiple technologies that can enable the actual virtual tour mechanisms.
Virtual Tours Demo