An ambrotype is a special kind of photograph that was popular a long time ago, before people had digital cameras.
To make an ambrotype, a photographer would first clean and then polish a piece of glass until it was really shiny. Then they would put a special kind of liquid on the glass, and put it in a special kind of camera that didn't use film.
Next, the photographer would take a picture of the person or thing they wanted to make into an ambrotype. They had to be very still because the camera took a little bit longer than modern cameras and if they moved, the picture would be blurry.
After the picture was taken, more special liquid was used to develop the image on the glass, making a negative. But don't worry, it's not a bad thing! Negatives are like the opposite of normal pictures, where light and dark areas are switched around.
The photographer would then turn the glass over and put it onto a dark piece of paper, which made the negative look like a positive picture. The final result was a one-of-a-kind ambrotype picture that was really special because it looked different from regular pictures.
Nowadays, people mostly use digital cameras to take pictures, but some people still like to make ambrotypes as a special kind of art.