Imagine you and your friends are playing a game of tag. Each of you is wearing a different color t-shirt to help you tell each other apart. Now, let's say that instead of playing outside, you are all standing in a big room.
In the room, you notice that there are other groups of people playing different games, but they are also wearing color-coded clothing. This means that if you were to run up to one of those groups and tag someone, you might accidentally tag the wrong person if they are wearing a similar color to your friends.
This is kind of like what happens with CDMA frequency bands. Instead of people wearing color-coded t-shirts, there are different electronic devices trying to communicate with each other using radio waves. In order to keep all of these devices from getting confused and interfering with one another, they are assigned to different frequency bands.
These bands are like sections of the room where only certain devices are allowed to communicate. If two devices are trying to talk on the same frequency band, they might end up interfering with each other, just like if two kids tag the same person by accident.
So, different CDMA devices are assigned to different frequency bands in order to avoid interference and make sure that only the intended parties can communicate with each other. This helps to keep communications clear and efficient.