ELI5: Explain Like I'm 5

Pin-up girl

A pin-up girl is like a pretty lady in a picture. She's usually wearing fun and sexy clothes, like shorts or high heels. The picture is often taken from a camera and printed on paper. People like to put the picture on walls or in calendars. It's like having a fun and pretty decoration for your home or office. It's a kind of art and some people like to collect them. They became popular in the past and are still popular today. So, it's like a picture of a cool and pretty girl that people like to look at and admire.