Okay, let's imagine we are going to a candy store and we want to buy a candy bar. The store has a lot of candy bars and wants to keep track of which ones they sell and how many they have.
To help with this, they use a special code called a GS1-128 barcode. This barcode has a lot of little lines and numbers that are unique to each candy bar.
When we buy the candy bar, the cashier scans the barcode with a special machine. This machine reads the lines and numbers on the barcode and tells the store's computer which candy bar we bought.
This helps the store know how many candy bars they have left in stock, and also which ones are popular with customers.
So basically, GS1-128 is a special code that helps stores keep track of what they are selling and how much they have of it.