Panoramas are multiple images merged together.
It's a way to create wider views of an area you want to cover.
You start to shoot from left to right (sometimes backwards as well). Most common way to photograph panoramas is to hold the camera vertically, but it works as good when the camera is horisontal. Vertical requires more images, while horisontal require multiple lines (upper and lower) to cover as much as vertical panoramas do.