"Place code" is like a secret code that tells your computer where to put things on the screen. Just like how you might tell a friend to place a toy in a certain spot when you're playing, a programmer uses place code to tell the computer where to show a picture or some words on a website.
The place code looks like a set of instructions written in a language that only the computer can understand. It might say something like "Put this picture in the middle of the page, two inches from the top." The computer then does what it's told and shows the picture exactly where the place code says it should be.
Programmers use place code to make sure everything on a website is arranged just right. They might use it to make a button go in one spot, while a picture goes in another spot, and words go in another spot. Place code helps make sure everything looks neat and organized on the screen, just like how you might keep your toys organized in your room.