First thing that needs to be clear: 360-degree video is not Virtual Reality (VR). So what is the difference?
The difference is not really that difficult. Sarah Ullman created a simple infographic that explains the biggest differences.
In a VR experience, there is a environment where you can move around. Usually these world are created in digital world, like most video games are. Moving physically around will also move you around in the VR experience, as long as you are not connected to a computer with your headset that restricts your movement. And maybe the most important part is that the storyteller does not have control over where you are going. You are free to discover the world that is created for you.
In a 360-degree video you are bound to the location that the camera is placed, but you can look freely around. 360-degree video experiences are created with cameras, 360-degree cameras. It is a film you are watching in an immersive experience. Different from a VR experience, is that there is a timeline in the 360-degree video, just like any other film. Because in a VR experience you can move around, take as much time as you like in the environment, the story goes on when you go on.
If you take the point of photography for example, you see a clear diffrence. Since in VR the world are created digitally, the photograph will be a still of a digital world. Where as a 360-degree camera can capture a photograph of the real world.
The point that they both have in common is that the storyteller has to capture the viewers attention. The user should be directed and motivated to look at a certain thing in the story. This can be done with sound or visual clues for example.
Since they are different, they are also on different platforms. With VR you have to buy the VR headset to support the VR experience, you need it to run the program/game. One could compare this to buying a new video game console, nowadays they have about they same price tag on them. 360-degree videos are almost all accessible online. Websites such as YouTube and Facebook support 360-degree videos and can be accessed on almost any device. You could also buy a special glasses/headsets to watch 360-degree videos. They are very similar to VR headsets. But with these you put your phone in the headset horizontally and watch a 360-degree video. When you move your head around, you will also look around in the video. Where as if you would watch this on a computer, you would have to drag around with you mouse to look around.
So to put it bluntly, the biggest difference comes down to this: In VR you are in control of the experience and in a 360-degree video you are an observer.