photo by Duncan Rawlinson
Panoramas or Panoramic photography is simple a technique of photography that captures images with relatively wide or elongated fields of view. The term panorama has also been applied to an image that happens to be cropped to a very wide aspect ratio.
To be clear there is no widely accepted separation between panorama and wide angle photography. Wide angle often refers to a type of lens and yet this lens type doesn't always create panoramas.
How do you know what is and what isn't a panoramic image? As a rough guide just consider that a photograph with a field of view approximating, or greater than, that of the human eye would may be considered panoramic. What is the field of view of a human? About about 160° by 75°.
What this boils down to us often an aspect ratio of 2:1 or larger. Or in plain english where the photo is at least twice as wide as it is tall. The photographs that results from these wide aspect ratios often look like a wide rectangle. In fact some panoramic photos have aspect ratios of 4:1 or even 10:1. Many panoramas even cover fields of view of up to 360°.
Thus, both the aspect ratio and coverage of field are important factors in determining whether or not an image is truly a panoramic image.
Here is an article on the history of Panoramas.
Learn how to make a Panorama