An albumen print is a special type of photograph that was really popular in the olden days. When people took pictures back then, they couldn't just do it on their phone; they had to use a special camera and special materials to make the picture. One of the most popular ways was to make an albumen print.
Here's how it works: first, the photographer takes a photo using a camera. Then, they mix together a special liquid that is made from egg whites (which they call albumen), salt, and some other stuff. They spread this liquid onto a piece of paper that has been coated with a special kind of salt. When the paper is dry, they put it in contact with the negative from the photo they took earlier. Then, they shine a bright light onto it for a little while, and voila! A picture appears on the paper.
Albumen prints are really cool because they have a lot of detail and look almost like paintings. They can also last a really long time if they're stored carefully. But since it takes a lot of time and special materials to make one, and people have easier ways to take pictures now, albumen prints are pretty rare these days.