Okay kiddo, have you ever been to a scavenger hunt where you have to look for certain signs or markers to find things? Well, something similar is used in a video game or a film to help the creators know where the different characters and objects should be placed in a scene. These markers are called "ob markers".
Think of it like a treasure hunt where the creators need to know where to hide the treasure. They use ob markers to remember where to put different things in a game or a movie. These markers basically serve as a reminder for the creators on where to position all the different characters, props, and objects in a scene.
So, ob markers are like small signs that help the creators of a game or a movie remember where everything should be placed. They are important because without them, the whole scene would look like a mess and the story wouldn't make much sense.