Ambisonics is a full-sphere surround sound format: in addition to the horizontal plane, it covers sound sources above and below the listener. From the Wiki -page – Ambisonics can be understood as a three-dimensional extension of M/S (mid/side) stereo that adds additional difference channels for height and depth.

Using or listening to ambisonic files will require specific software to listen to and edit ambisonic files. It also requires a multi speaker setup to enjoy listening back properly, though you can compromise with headphones and convert the files to a binaural version to get a sense of the Ambisonic experience. There are many resources you can access to learn more and find software to use. This very short list highlights the resources, people, and software that I have been using over the last few years.