Sticky notes function
The sticky back of the post-it note allows you to write down what you want to do, then tear it off and post it where you can see it and remind yourself of your to-do list. It can also be used to inform people, very convenient. That's why it's called post-it notes.
For the sake of beauty, there are more and more styles and colors for the convenience stickers nowadays.
Sticky notes are convenient. You can carry it in your bag or book. It's easy to deal with things you tend to forget but want to remind yourself of.